A bitcoin futures market is different from any other futures market because the liquidity of bitcoin is perceived to be difficult but the traditional folks on Wall St. The futures may be manipulated in large form, but will the real price of bitcoin be manipulated as much? No.
Another characteristic of bitcoin that will dilute the impact of futures speculation is the fact that this is truly a world market, a global market. The spot price isn't set through one or two central markets.
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The manipulators are going to have a real hard time of it as long as so many exchanges around the world are trading bitcoin 24/7.