IANAL but after 5 min of googling Mt. Gox...

Things you'd have to consider if you're an US citizen...

1. Is the company in question incorporated or do significant business in the U.S. (seems like they were at least something in the U.S., filed for BK in Dallas)
2. Statute of limitations
3. Your contract or whatever agreement you signed/agreed to when using their service
4. They filed BK, so are you able to pierce the corporate veil?

The Bad: You weren't a creditor, you're probably going to have to show fraud or that they intermingled their personal business and the company's business, you're going to have to hope your state's SoL didn't expire (assuming you're in the U.S.), etc. Also seems like they have a bunch of creditors clamoring for money.

The Good: I assume you're posting this because of the huge upward valuation of bitcoin and the fact that the Japan BK court and other non-Japanese courts will be considering whether the new valuation of BC means that the company should lose their BK protection. No way I'll try and predict that, though I'm sure there's plenty of case law to guide you (or a corporate BK attorney :P). If they are moved out of BK, yeah you probably can file a suit and see if you can get your money. There's also a good 99% chance that some law firm already has filed a class-action lawsuit against them. In class actions, you can either (a) contact them and become a named plaintiff (probably unlikely) or (b) just sit on your ass, hope they win or settle, and the law firm ends up contacting you asking if you would like to join in the class action and get $X money, or you can choose to file your own lawsuit.