While I think we all recognise that the Mt.Gox team has not covered themselves with glory, you have to think about incentives when talking about criminal activity.
Mt.Gox was legitimately pulling in tens of thousands of dollars a day.
Once the exchange is up and running and is secure, it is a license to print money.
How much would they make from stealing balances? Factor in as well that they would be international criminals as well.
I think on balance, a legitimate three million dollar a year business is worth more than the temporary winnings from any crime they could commit. Given the growth potential of Bitcoin, it is conceivable that being the first and most established exchange could also end with them earning billions not millions.
Every day that Mt.Gox is switched off is costing them thousands of dollars in lost trading fees; not to mention lost reputation and good will. I guarantee that they are killing themselves to try and get back online. I would be.
Typically in these scenarios the owners dont set out to be crooks.. they dip into the funds with the intention of 'putting the money right back'.. then something goes wrong, like i dont know, like this major hack, or a law suit, cease and desist letter from the japanese money laundering authority, whatever.. some unforseen circumstance. Also, the writing is on the wall here... the days of easy money are over.. BEST CASE scenario if mt gox even recovers at all will be a fee war with trade hill, severely diminishing margins. Their best days could very well be behind them. And that 0.65% (lower now) and diminishing volumes as they share their pie with tradehill... fee compared to 100% theft is a 300:1 ratio or so.
Logically presented with this opportunity I personally could see the temptation with 2 alternatives, one a bankrupt mt gox with a difficult legal future, with stiff competition from tradehill, and potential legal threats from authorites.. and a one time score.
you dont get it.. the very access to the money is a corrupting feature that history has PROVEN very few people are above, this is why these regulations have ssprung up over the years.. I bet you even bernie madoff started out totally legit.