They failed to maintain their business. Contracts have been made and settled although there were devious parties involved but they aren't under the company's jurisdiction. Mt. Gox isn't a security force. They are an escrow. No vigilant justice should occur.
Instead of voiding people's trading contracts at large why doesn't Mt. Gox just hold itself liable and pay for the losses it caused directly? Why doesn't Mt. Gox just accept its failure? Why burden innocent traders for its negligence?
Again, personally, I think Mt. Gox should just be wiped off the map. They're done. They failed.
I can understand your point. Personally I think the same of United and American Airlines after 9/11.
Who should be the arbiter? The current and future customers of Mt. Gox.
If Mt. Gox handles this well then they will have the confidence of their users.
If they handle it poorly, they will lose confidence and business.
So the ball is really in their court. Do they want to stay in business?
Their actions will soon tell and customers will decide if their actions go far enough.