Might sound silly but is there ANY chance mt.gox could shutdown and run off with our money worst case?
Why would you worry about that? Has anything like that ever happened before?
Let's see:
Savings and loans
Enron
Tyco
Worldcomm
Bernie Madoff
CMO's
AIG
Lehman Brothers
Sub prime mortgage crisis
Greek bonds
Cyprus banks (which started the massive run up past $50 on March 17th)
Perhaps they wont "run off" but, not knowing Japanese law I don't know what prevents them from shutting down and declaring bankruptcy or something similar. I'm not sure US citizens would have much luck getting their money back whatever the law is there.