This is exactly why regulations exist. MtGox should need to register as a Money Service Business (MSB) in the US and as a Money Transmitter in each state that they support. That needs to happen even if they're not a US company. The same applies to the EU, Australia, Canada, and many other countries that have regulations around this kind of activity.

The purpose of the regulations are to protect consumers for companies that are either malicious or incompetent.

The problem is that the licensing process is expensive, painful, and long. There should be better ways. Nonetheless, there's a reason why the exist.