Entirely possible; I'm writing these before bed after getting home from work. I just have a feeling that if someone tried to convert 2% of the world's USD to rubles in a few seconds without an equivalent transfer in the opposite direction everything would explode. MtGox not being able to handle a transaction like this simply means that there was less than 500k flowing in the opposite direction every ten minutes. If there were, that would imply either a spectacular amount of arbitrage or enough transactions going on inside bitcoin for people to be changing 500k back and forth every ten minutes. This crash just means that neither of those are happening, which I find entirely believable.