You probably heard about this story:
http://www.virtualcurrencyreport.com/2014/02/two-florida-users-of-localbitcoins-com-arrested-for-money-laundering-and-unlicensed-money-transmission/There are a couple of things to take away from this article.
1) "Where a seller of bitcoin knows (or has reason to believe) that the transaction involves proceeds derived from or to be used in furtherance of illegal activity, this could separately result in charges under state anti-money laundering laws."
The undercover agents reportedly very explicitly stated that they intended to use the proceeds to pursue illegal activities. Helping someone commit a crime is, of course, illegal which is one reason they were charged.
2) "...
Florida law enforcement has determined that engaging in the business of direct sales of bitcoin in
Florida or to
Florida residents requires a
Florida money services business." (Emphasis mine.)
Each state has their own money transmission laws and they do not necessarily coincide with every other state. At the Texas Bitcoin Conference, Russell Reese,
Director of the Texas Department of Banking, specifically stated that Texas has no official standing on virtual currencies but that individual, person-to-person trades DID NOT constitute money transmission. (Interestingly, this was in regards to a question about Bitcoin ATMs and he indicated that even if one used a machine to facilitate selling
your own bitcoins, it was still considered a "person-to-person" exchange.)