Isn't that the same with Mt. gox? How do you get the money to them without going through a bank?
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...
Whether those regulations are actually effective is questionable (see HSBC, BoA, etc.), but that's the rationale.