BTC-E owes the community a detailed explanation on how BTC was pushed to 150 USD on volume that can't possibly justify that move, and explain the cancelled orders others have reported here.
There's plenty that needs explaining. And if BTC-E wants to garner any kind of trust they would be forthcoming. So far, nothing!
The volume CAN justify that move. That's because it's a flash crash. Someone might've market sold 3k BTC and it triggered stop-losses that amounted to 8k. It is possible because it happens really fast and then the price is back up again with little volume. Blame the thin orderbook.
On the other hand, real plunges are gradual and can continue for hours and thus have a lot higher volume transacted just due to their duration.
It can happen if open orders were cancelled without the users consent, as has been reported here. Opening the way for a bear attack, pushing critical stop points.... either by collusion, or by some software glitch, that is exactly what happened. Either case, users that had their stops hit, and users that had their open orders cancelled were defrauded. This was not a market move according to free market forces.