Is this latent damage from the IRS ruling or something? I don't know why I'm still surprised by sudden, massive movement in BTC price, but usually the reasons seem pretty obvious (and over-reported).
It is good that the price is going down since more people will buy Bitcoin now.
Also, probably more importantly, Mt. Gox was constantly pushing the prices higher because nobody could withdraw USD, so the only way to get out of Mt Gox was to use all your USD to buy bitcoins and then transfer them to another exchange.