Maybe speculators are quitting the market and going elsewhere
I guess that's the difference between investing and speculation.
Investing means putting your money into something over which you have some control or in which you strongly believe.
Speculation is gambling on someone else's performance, whether it's lottery tickets, shares in companies without a controlling interest, numbers on a roulette wheel, or horse races. Sure, if you know your horses and jockeys (or companies and directors), you might make enough to cover the vigorish charged by the track (or stockbroker), but it's still gambling unless you're the jockey or CEO.
People who invest in Bitcoin because they strongly believe in it tend to be hoarders who won't sell lower than they paid because they firmly believe it will eventually keep going up.
Speculators will try to take advantage of every movement, up or down doesn't really matter.
As I mentioned elsewhere, the bulk of my bitcoins are hoarded for investment because I think Bitcoin and secure peer-to-peer networking are the future, while some are set aside for day-trade speculation. Others have already been spent on shares of Canadian Bitcoin exchange Virtex so I can hopefully get a piece of that vigorish.
Needless to say, I'd prefer them to increase in value.