losing the money was not the crime, trying to cover it up and engage in dubious practices like using customer fiat funds to shore up your company, buy btc (on gox at $150) to sell on other exchanges (bitstamp at $500) is likely to be the root of their legal woes not that they wer ehacked and lost 750k coins.
Their cover up is what will bring legal repercussions.
I have no idea how accurate this is, but Mark seemed to believe they were "operating within the law":
"Karpeles replied that the matter is “confidential,” adding that the company had discussed its business model with Japanese authorities “to ensure that we are operating within the law here.”"
Their cover up is what will bring legal repercussions.