There are definitely some sharks who will use this opportunity to play the market. Considering how CME is a mainstream institution, it will bring in a lot more people into the btc exchanges, people who will look at btc only as an investment and nothing else. If large sharks come into play, we can see the manipulation happen at larger levels and larger price ranges that we know. Its a silver lining, because while more people will enter the btc market, they dont all care about its potential as a currency or its underlying technology.