Unlikely, because it's not logical. mtgox was raking in millions in trading fees every month, all it had to do was maintain their very strong #1 market share position. Why would mtgox take on HUGE risk in unauthorized short selling with customer funds? because if they lose, not only they will lose a lot of money, their cashcow (the #1 bitcoin exchange) will also be dragged down with it.
That's exactly what I thought. It could have been more of a snowball effect. Karpeles has been in bitcoin since it was trading for less than a dollar. He decides that people buying at over $100 are paying too much. He decides to short SOME waiting for the price to decline to cover the short. The next thing he knows the price just keeps going higher and higher. Now he's chasing, shorting more and more. He never meant to be so short, and now he's being squeezed as people are withdrawing cash and bitcoin.