One of the exchanges I use is cryptsy.com, which apparently does not deal in fiat currency. I would say they get a decent amount of business.
Actually, cryptsy.com is already registered as an MSB - from their TOS:
"BSA / FinCEN
Cryptsy is registered with the BSA as an MSB (Money Services Business). Cryptsy may be required to file details of account activity to this organization from time to time."
Looks like a quite a busy site, though
