Hey, first off, I'm new here so be gentle..
I'd like to spread a suggestion to MtGox, in case they really lost the money.
In this case suing will likely not be helpfull at all apart from taking revenge of course. But if people at MtGox have not run away I would think it would be more usefull with preceed to something like the following.
They open a new exchange on a new site and everybody having had deposits at MtGox will be like a shareholder to the mew exchange, participating to the income generated by it.
On the long run, this could bring the money back, which suing and jail time will not.