•   A decline in the adoption of bitcoin could have a negative effect on the price of bitcoin and bitcoin-related investments. Bitcoin’s adoption has been on a generally continuous climb since bitcoin first gained mass media attention in 2013. However, there can be no guarantees this growth will continue. Further, adoption of bitcoin as a means of payment has been limited when compared with the increase in the price of bitcoin, indicating that the majority of bitcoin’s use is for investment and speculative purposes. A lack of acceptance of bitcoin as a means of payment could negatively impact the price of the Bitcoin Futures contracts in which the Fund invests.

•   Tax Risk — In order to qualify for the special tax treatment accorded a regulated investment company (“RIC”) and its shareholders, the Fund must derive at least 90% of its gross income for each taxable year from “qualifying income,” meet certain asset diversification tests at the end of each taxable quarter, and meet annual distribution requirements. The Fund’s pursuit of its investment strategies will potentially be limited by the Fund’s intention to qualify for such treatment and could adversely affect the Fund’s ability to so qualify. The Fund can make certain investments, the treatment of which for these purposes is unclear. If, in any year, the Fund were to fail to qualify for the special tax treatment accorded a RIC and its shareholders, and were ineligible to or were not to cure such failure, the Fund would be taxed in the same manner as an ordinary corporation subject to U.S. federal income tax on all its income at the fund level. The resulting taxes could substantially reduce the Fund’s net assets and the amount of income available for distribution. In addition, in order to requalify for taxation as a RIC, the Fund could be required to recognize unrealized gains, pay substantial taxes and interest, and make certain distributions.
Assume it is January 3, 2015. Bob and Ann both want to trade at Bitcoin Futures Exchange (BFE). BFE offers 3 different contracts: one expiring and settling on Friday January 9 ('weekly'), another expiring Friday January 16th ('biweekly'), and finally one expiring in March 27 ('quarterly').  Each contract is worth 1 bitcoin notionally.  BFE has a policy that traders have to put 20% of margin down to enter a trade, so Bob and Ann deposit 0.2btc to their BFE accounts as they only want to trade 1 contract.

You’ll find that different exchanges cater to different markets. Today, most countries have at least one cryptocurrency exchange specializing in their own currency. There are exchanges that can accept New Zealand Dollars in exchange for bitcoin, for example. Other exchanges are known for certain pairs. Bithumb, for example, has particularly strong liquidity in the ETH/KRW (South Korean Won) pair at the moment (and it’s easily the most popular cryptocurrency exchange in Korea).
The introduction of futures didn't lead to a wave of hedge-fund money shorting bitcoin. It led to retail and institutional money going long bitcoin. We talked last week about the spread between Cboe's bitcoin futures price and the actual price of bitcoin, which was wider than $1,000 for a while. The spread has tightened considerably -- as of 8:15 a.m. today, the CME futures traded at $18,585, Cboe futures at $18,670, and spot bitcoin at about $18,245, for a spread of about 2 percent -- but it still exists. Why would you pay more for a synthetic bitcoin in a month than you would for an actual bitcoin today? The answer, presumably, is that the synthetic bitcoin is more valuable to you: You want bitcoin exposure, but you'd prefer to get it through a standardized contract on a regulated exchange that settles in dollars. 
When the Fund has an open futures contract position, it is subject to daily variation margin calls that could be substantial in the event of adverse price movements. If the Fund has insufficient cash to meet daily variation margin requirements, it might need to sell securities at a time when such sales are disadvantageous. Futures markets are highly volatile and the use of or exposure to futures contracts may increase volatility of the Fund’s NAV. Futures contracts are also subject to liquidity risk.
There's a lot of ins and outs which can get confusing in arbitrage trading. We won't go into the technicals of why futures contracts trade at a premium to spot price. You can read a full explanation here. If it's not of interest to you, all you need to know is that there's a tendency, the further out in time the futures contract expires, for the premium to spot to be higher and higher in nominal percentage terms.