Wouldn't it be the responsibility of Mt.Gox and Dwolla to submit the required forms? Unless you are saying you think having money in Mt.Gox qualifies as a foreign account and he should have filed an FBAR.
I'm not a financial expert by any means but it's pretty clear when you're moving cash to Mt. Gox, you're moving it out of the country. And I think the paperwork is a joint responsibility.
That's mostly likely why DHS has shut them down.