What if..
.. MtGox got hacked like a year ago, with BTC stolen, and they were too chicken to announce it, instead thinking: "Well, we make good money don't we.. maybe if we just keep going, then maybe we could earn back the money we lost."
But after a year, everything has just went over their heads and they are insolvent.
That is the only reason that I can imagine of. Other then the theory that Gox is operated by an flock of drunken emus.
It might be something of that nature. Or they want the exchange to shutdown but want to keep all the fiat in a "legal" way. They hope that all coins will be taken off the exchange and then they will shut down the exchange. The reasons could be many, maybe they got hacked like you said or they have serious problem they can't deal with.
