The pricing in of gox's failure began all the way back in May and June, when investors could not withdraw fiat, funds were seized by DHS, and there was the lawsuit with coinlab. At that point, investors probably assumed that all their fiat was missing and that gox was insolvent, since they couldn't withdraw, and the pricing in began. This caused a crash from $130 to $66, until offline investors decided that was a good price and led a recovery. Bitstamp rapidly grew in August with the orderbook growing exponentially every day, and during the breakout in October it was well known that Bitstamp was where true liquidity interchange in U.S.D. was occuring and that gox was no longer relevant. Gox became a joke. "emptygox". Gox probably put a nice damper on the entire rally, and we might have gone higher without it.
Just recently, gox led another crash. The drop from $800 began when users started having issues withdrawing bitcoin from gox. At the moment when gox announced their malleability issue and it became official that users could neither withdraw fiat nor btc, all hope in gox became lost. Gox was now truly insolvent, as you could not withdraw ANY funds. This became especially apparent once every other exchange had fixed their malleability issue, in one day, EXCEPT gox, who was at two weeks and counting. The death spiral of prices on gox all the way to $88 was continually confirming everyone's suspicions - that kind of price action would not be happening unless something was seriously wrong. Nobody would sell their bitcoins at 15% of the real value of a bitcoin unless they were SURE gox was insolvent. So this action led a crash in prices all the way from $800 to $530 and below. When the website went down, prices crash all the way down to $400. That's a 50% loss from $800, on top of all the previous crashes gox had driven.
Prior to gox's recent bankruptcy announcement, it was about 90% certain to anyone with a brain that all of gox's customer funds had been lost, and this had already been getting priced in to the bitcoin price for nearly a year. The bankruptcy announcement simply turned a 90% certainty into a 100% certainty. Big deal... Maybe it will cause a little dip, but not a huge crash like everyone is calling for - that already happened, multiple times.
+1
And that this story about gox is for the textbooks how prices are always smarter than one person (price = most efficient way to aggregate informations -> Hayek).
But informations can change quickly and so the price does.
+ because of panics, day traders and still not perfect information the price signal can be distorted, for sure.