Right. So far, the regulatory framework has it's pivot foot in fiat. That is, crypto-to-crypto exchanging and dealing doesn't seem to be the topic of any MSB regulation at all.
Well lack of enforcement doesn't mean there won't be future enforcement.
Per FinCEN they at least believe Virtual Currency exchanged for other Virtual Currencies fall under their domain.
An exchanger is a person engaged as a business in the exchange of virtual currency for real currency, funds, or other virtual currency.
....
The definition of a money transmitter does not differentiate between real currencies and convertible virtual currencies. Accepting and transmitting anything of value that substitutes for currency makes a person a money transmitter under the regulations implementing the BSA.
http://fincen.gov/statutes_regs/guidance/html/FIN-2013-G001.htmlSeems an over reach to me but they are the ones with all the guns (and monopoly on lawful violence).
(Note this was a surprise to me too. Missed it in the first reading back in March. I noticed it when looking up a different cite for the post above and updated my incorrect post.)