Margin Call - when you run out of bitcoin on your account to cover the contract positions you have taken (your account value doesn't cover the Maintance Margin) you are officially rekt. Some exchanges like CryptoFacilities will merely notify you that you have to deposit more or reduce your positions to increase your margin. Others like BitMEX will liquidate you at this level where the exchange takes over your position to liquidate it into the market to prevent system loss.
Notwithstanding the guidelines set forth above, S&P 500 Dividend Aristocrats ETF, S&P Midcap 400 Dividend Aristocrats ETF, Russell 2000 Dividend Growers ETF, and DJ Brookfield Global Infrastructure ETF will not borrow money for investment purposes. Each of these Funds may borrow money as a temporary measure for extraordinary or emergency purposes, including to meet redemption requests or to facilitate the settlement of securities or other transactions, in an amount up to 10% of its respective net assets.
Under normal market conditions, each Fund intends to invest substantially all of its assets in Benchmark Futures Contracts. The contractual obligations of a buyer or seller holding a futures contract to expiration may be satisfied by settling in cash as designated in the contract specifications. Alternatively, futures contracts may be closed out prior to expiration by making an offsetting sale or purchase of an identical futures contract on the same or linked exchange before the designated date of settlement. Once this date is reached, the futures contract “expires.” The Funds do not intend to hold bitcoin futures contracts through expiration, but instead to “roll” their respective positions. “Rolling” refers to a process whereby futures contracts nearing expiration are closed out and replaced with an identical futures contract with a later expiration date. Accordingly, the Funds are subjects to risks related to rolling.

The term altcoin has various similar definitions. Stephanie Yang of The Wall Street Journal defined altcoins as "alternative digital currencies,"[25] while Paul Vigna, also of The Wall Street Journal, described altcoins as alternative versions of bitcoin.[26] Aaron Hankins of the MarketWatch refers to any cryptocurrencies other than bitcoin as altcoins.[27]
expect that the futures exchanges, through information sharing agreements, will be monitoring the trading activity on the relevant cash platforms for potential impacts on the futures contracts’ price discovery process, including potential market manipulation and market dislocations due to flash rallies and crashes and trading outages. Nevertheless, investors should be aware of the potentially high level of volatility and risk in trading these contracts . . . it is incumbent on market participants to conduct appropriate due diligence to determine the particular appropriateness of these products, which at times have exhibited extreme volatility and unique risks.”
To the extent that an Underlying RIC realizes net losses on its investments for a given taxable year, a Fund that invests in the Underlying RIC will not be able to benefit from those losses until (i) the Underlying RIC realizes gains that it can reduce by those losses, or (ii) the Fund recognizes its share of those losses when it disposes of shares in the Underlying RIC. Moreover, when a Fund makes such a disposition, any loss it recognizes will be a capital loss. A Fund will not be able to offset any capital losses from its dispositions of shares of the Underlying RIC against its ordinary income (including distributions deriving from net short-term capital gains realized by the Underlying RIC). In addition, a portion of such capital loss may be long-term, which will first offset the Fund’s capital gains, increasing the likelihood that the Fund’s short-term capital gains will be distributed to shareholders as ordinary income.
If I held the opinion that an asset was going to go one way, but then made the research and it turned out that I started thinking it might actually be headed the other way, I should feel no obligation to hold on to my original opinion, just because I didnt want to feel I’ve been initially wrong. This seems obvious but is much tougher in practice for inexperienced investors.
You may wonder: where do these contracts come from? We know on the spot market that bitcoins are being bought and sold for fiat, but how the heck are bitcoins being used to trade bitcoin futures contracts? Let's walk through a really simple example showing how an exchange functions when there's just a simple two traders who want to go long and short. 
The rules regarding the extent to which such subpart F inclusions will be treated as “qualifying income” for purposes of the 90% gross income requirement described above are unclear and currently under consideration. In the absence of further guidance, each Parent Fund will seek to ensure that it satisfies the 90% gross income requirement, including but not limited to by ensuring that its Subsidiary timely distributes to it an amount equal to the Subsidiary’s subpart F income by the end of the Subsidiary’s taxable year. In order to make such distributions, the Subsidiary may be required to sell investments, including at a time when it may be disadvantageous to do so. If a Parent Fund were to fail to qualify as a RIC accorded special tax treatment in any taxable year, it would be subject to tax on its taxable income at corporate rates, and all distributions from earnings and profits, including any distributions of net tax-exempt income and net long-term capital gains, would be taxable to shareholders as ordinary income. In addition, the Parent Fund could be required to pay substantial taxes, penalties and interest, and to make substantial distributions, in order to re-qualify for such special treatment.
These developments are expected to not only further rally the price of Bitcoin, but also open the doors for more traditional investment opportunities based on cryptocurrencies, such as a Bitcoin exchange-traded fund (ETF). ETFs are currently very popular investment products for beginning and advanced investors because they charge low fees and usually have low volatility. Because high volatility is one of the factors preventing conventional investors from entering the crypto market, products such as these could offer them the best of both worlds.

The method by which Creation Units are created and traded may raise certain issues under applicable securities laws. Because new Creation Units are issued and sold by the Trust on an ongoing basis, at any point a “distribution,” as such term is used in the 1933 Act, may occur. Broker-dealers and other persons are cautioned that some activities on their part may, depending on the circumstances, result in their being deemed participants in a distribution in a manner which could render them statutory underwriters and subject them to the prospectus delivery and liability provisions of the 1933 Act. For example, a broker-dealer firm or its client may be deemed a statutory underwriter if it takes Creation Units after placing an order with the Distributor, breaks them down into constituent Shares and sells some or all of the Shares comprising such Creation Units directly to its customers; or if it chooses to couple the creation of a supply of new Shares with an active selling effort involving solicitation of secondary market demand for Shares. A determination of whether a person is an underwriter for the purposes of the 1933 Act depends upon all the facts and circumstances pertaining to that person’s activities. Thus, the examples mentioned above should not be considered a complete description of all the activities that could lead a person to be deemed an underwriter. Broker-dealer firms should also note that dealers who are effecting transactions in Shares, whether or not participating in the distribution of Shares, are generally required to deliver a prospectus. This is because the prospectus delivery exemption in Section 4(3) of the 1933 Act is not available in respect of such transactions as a result
A Fund may invest in one or more exchange-traded funds that invest in commodities or options, futures, or forwards with respect to commodities, and are treated as QPTPs for federal income tax purposes. As noted above, a Fund is limited to investing no more than 25% of the value of its total assets in the securities of one or more QPTPs. Although income from QPTPs is generally qualifying income, if an ETF intending to qualify as a QPTP fails to so qualify and is treated as a partnership for U.S. federal income tax purposes, a portion of its income may not be qualifying income. It is also possible that an ETF intending to qualify as a QPTP will be treated as a corporation for federal income tax purposes. In such a case, it will be potentially liable for an entity-level corporate income tax, which will adversely affect the return thereon. There can be no guarantee that any ETF will be successful in qualifying as a QPTP. In addition, there is little regulatory guidance concerning the application of the rules governing qualification as a QPTP, and it is possible that future guidance may adversely affect the qualification of ETFs as QPTPs. A Fund’s ability to pursue an investment strategy that involves investments in QPTPs may be limited by that Fund’s intention to qualify as a RIC, and may bear adversely on that Fund’s ability to so qualify.

The Distribution and Service Plan is intended to permit the financing of a broad array of distribution-related activities and services, as well as shareholder services, for the benefit of investors. These activities and services are intended to make the Shares an attractive investment alternative, which may lead to increased assets, increased investment opportunities and diversification, and reduced per share operating expenses. There are currently no plans to impose distribution fees.

Each Fund may engage in transactions in index options listed on national securities exchanges or traded in the OTC market as an investment vehicle for the purpose of realizing the Fund’s investment objective. The exercising holder of an index option receives, instead of the asset, cash equal to the difference between the closing level of the index and the exercise price of the option. Some index options are based on a broad market index such as the Standard & Poor’s (“S&P”) 500® Index, the New York Stock Exchange, Inc. (“NYSE”) Composite Index or on a narrower index such as the Philadelphia Stock Exchange Over-the-Counter Index. Options currently are traded on the Chicago Board Options Exchange, the NYSE Amex Options and other exchanges (collectively, “Exchanges”). Purchased OTC options and the cover for written OTC options will be subject to the relevant Fund’s 15% limitation on investment in illiquid securities. See “Illiquid Securities” below. When required by law, a Fund will segregate liquid assets in an amount equal to the value of the Fund’s total assets committed to the consummation of such options. Obligations under options so covered will not be considered senior securities for purposes of a Fund’s investment restriction concerning senior securities.

ProShare Advisors believes that its compensation program is competitively positioned to attract and retain high-caliber investment professionals. The compensation package for portfolio managers consists of a fixed base salary, an annual incentive bonus opportunity and a competitive benefits package. A portfolio manager’s salary compensation is designed to be competitive with the marketplace and reflect a portfolio manager’s relative experience and contribution to the firm. Fixed base salary compensation is reviewed and adjusted annually to reflect increases in the cost of living and market rates.
To illustrate the point, recall that futures markets are just counterparty contracts. Let's say I want to SHORT the market and profit off a decline in BTC/USD. If I put an order to sell Weekly futures contract at $400, and someone buys that offer, then we have created a futures contract. If it goes down, I profit and he loses, if it goes up, he profits and I lose. However, what if price goes down really fast, and my counterparty only had a little margin backing his position? Well, he gets margin-called when it goes down enough, and the system takes his contract and forces it to be sold to a different counterparty that wants to take the LONG side of my contract.
On 25 March 2014, the United States Internal Revenue Service (IRS) ruled that bitcoin will be treated as property for tax purposes. This means bitcoin will be subject to capital gains tax.[80] In a paper published by researchers from Oxford and Warwick, it was shown that bitcoin has some characteristics more like the precious metals market than traditional currencies, hence in agreement with the IRS decision even if based on different reasons.[81]
Now, if that margin-call does not get filled and the price continues to fall, then I'm making profits on my contract but nobody is paying for it since the counterparty who got margin-called didn't get the liquidation order filled. So what happens is that at settlement time of the contract, that unfilled liquidation loss to the system will be deducted from the profits of ALL traders before they are distributed.
participating in a distribution (as opposed to engaging in ordinary secondary market transactions), and thus dealing with the Fund’s shares as part of an “unsold allotment” within the meaning of Section 4(3)(C) of the Securities Act, will be unable to take advantage of the prospectus delivery exemption provided by Section 4(3) of the Securities Act.
RD – Restricted default. ‘RD’ ratings indicate an issuer that in Fitch’s opinion has experienced an uncured payment default on a bond, loan or other material financial obligation but which has not entered into bankruptcy filings, administration, receivership, liquidation or other formal winding-up procedure, and which has not otherwise ceased operating. This would include:

As an example: if you have Quarterlies contracts that you made profits on over the weekend, then this profit needs to be withheld because of the risk of socialised losses. By Friday, however, this profit is available to be withdrawn and the positions are all rebalanced. Technically this is not a "settlement", because if you are holding an open Quarterlies contract when the weekly settlement occurs, your position will remain open, it will just experience a step-up in cost-basis and the unrealised Pnl is applied, so that socialised losses can be handled.
Currently the front month future is the January contract which at last check could be sold for $17,600.  This contract settles in a cash transfer based on the 4:00 pm eastern bitcoin auction price on Wednesday January 17, 2018 established by Gemini who is partnering with Cboe Global Markets.  The bitcoin price at Gemini is close to $16,600 so I will use that for the underlying bitcoin price in this example. 
The global regulatory landscape for bitcoin and other digital assets has been inconsistent and continues to evolve. Some countries have taken an accommodating approach to the regulation of digital assets while others have banned their use. There are various accommodative approaches a country may take. Sweden and Australia treat bitcoin as a currency, while Canada and Taiwan have labeled bitcoin as a digital or virtual currency, distinct from fiat currency. Norway categorizes bitcoin as a form of virtual asset or commodity. The United Kingdom treats bitcoin as private money and determined that the value added tax will not apply to bitcoin sales, but it can be charged on the commission instead. In April 2017, legislation took effect in Japan that treats bitcoin and other digital assets as included in the definition of currency. In July 2016, the European Commission released a draft directive that proposed applying counter-terrorism and anti-money laundering regulations to virtual currencies, and, in September 2016, the European Banking authority advised the European Commission to institute new regulation specific to virtual currencies, with amendments to existing regulation as a stopgap measure. Regulatory bodies in some countries such as India and Switzerland have declined to exercise regulatory authority when afforded the opportunity.
In order to provide current Share pricing information, an Exchange disseminates an updated Indicative Optimized Portfolio Value (“IOPV”) for each Fund. The Trust is not involved in or responsible for any aspect of the calculation or dissemination of the IOPVs and makes no warranty as to the accuracy of the IOPVs. IOPVs are expected to be disseminated on a per Fund basis every 15 seconds during regular trading hours of an Exchange.
The CME Group contract (symbol "BTC") began trading on December 18, 2017, building off of the success of the BRR and demand for a regulated trading venue for the digital asset market. The contract is cash-settled, based on the CME CF Bitcoin Reference Rate (BRR) which serves as a once-a-day reference rate of the U.S. dollar price of bitcoin. Bitcoin futures are listed on and subject to the rules of CME.2

Since you bought 68.4246 BTC, you want to short 68 BTC and lock in the USD value. You will have 0.4246 BTC left over, which will give you a slightly long bias. You can either fix this by only buying 68 BTC in step 1 or by giving yourself more short exposure by shorting 69 BTC. Remember that CryptoFacilities contracts are inverse (which allow locking in USD) and are denominated in BTC
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