I did some research into money exchanging and money transfer regulations in the U.S.
The raw legal code is online at: http://www.access.gpo.gov/nara/cfr/waisidx_08/31cfr103_08.html
I am not a lawyer; trying to understand legalese is just an odd hobby of mine. From my reading of the regulations, if you exchange less than $1,000.USD worth of Bitcoin per day you don't have to worry:
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It looks to me like if you exchanged more than $1,000.USD per day a good lawyer might be able to argue that Bitcoins do not meet the legal definition of "currency":
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Then again, if Bitcoins are not legally "currency" then it might be left up to a Court to decide what, exactly, they are, and the result might be really unpleasant (if a judge decided that they're like stocks and are therefore subject to regulation by the Security and Exchange Commision you might find yourself in jail for being an unlicensed stock broker).
I think Bitcoin needs some licensed, regulated exchanges that abide by all the regulations, treating Bitcoins just like another foreign currency, and make it really easy to buy or sell a few hundred dollars worth of Bitcoins. The regulations are not as onerous as I expected; basically you just have to get identification from customers that make large transactions and report them.