I think it may be technically possible for Bitcoin to drop 90% in a single day and with most people unable to sell at any price if they want it settled on the block chain.
It could be Armageddon with nearly everyone holding bitcoint getting wiped out.
That MtGox guy should sell his billion of bitcoin soon, like right now. It is a hot potato right now and I wouldn't want to be left holding the bag with things go south.
I was a student in the first dotcom bubble and it was similar to this. And people predicted it would drop and then it did drop and basically wiped out the whole tech sector for nearly 3 years.
This is a very, very good thing. There are no breaks going up, therefore there should be no breaks going down. What's even better is that Bitcoin is 24/7 so there's not even the option of "waiting for the train to stop" when you're trying to get off.
The trading curbs are incredibly important because if there is false information and everyone rushes to the exit, people can be wiped out in the panic and then find out the next hour that nothing was true.
With bitcoin there will likely be settlement issues for days after a crash. It will be messy as hell.