The mt gox volume is about $300k a day. Any one of these people could sell $10k a day without making that much of a dent in the price (they used to have a $1k a day limit but I'm sure that's not foolproof).
That would be enough to liquidate even the largest portfolio in 8 months. Certainly if you were uneasy about the market, that's exactly what you'd be doing (and maybe they are).
The market is very thin, any large selloffs would make the price drop significantly.