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.

My understanding is that FinCEN is looking to regulate MSBs (money service businesses) that act as exchanges involving USD, which could be used to mask illegal money laundering.  It's hard to see how converting, say, MNC for NMC, means a whole lot of money laundering is going on.