A thought:
It appears that there will shortly be BTC futures. Several here expressed interest in shorting BTC and these futures will be the most obvious way to do it. There is presumably a lot of pent up shorting interest out there that will take advantage of this new way to short. That should create a lot of selling pressure and drive BTC down at least on the first day the futures are trading. Surely there will be future buyers as well, but most buyers have already bought actual BTC where as no short sellers have been able to sell yet.