I'm not really familiar with Mt. gox, but I'd assume you can send in a money order or perhaps even cash. I don't know anything about Dwolla either, maybe they have a method of bypassing banks? I might be wrong so if someone knows better please correct me.

Edit: Did a little bit of digging[1], looks like they accept wire transfers (e.g. Western Union), and I'm sure there would be ways through those e-currency and other services to deposit large amounts of unregulated money.

[1]https://support.mtgox.com/entries/20490576-Withdrawals-and-D...