I was looking at starting up a site that would sell bitcoins through credit card transactions as a US based business. Not wanting to run into immediate regulatory problems I gave FinCEN (Financial Crimes Enforcement Network) a call. It took them a couple of weeks to get back to me but the answer was yes that business would be required to register as a Money Service Business.
It's what I'd expect but I'm interested in the specific regulations they quoted. Knowing that gives an indication of whether they're currently regarding Bitcoin as a currency, a commodity or some other kind of financial product/service. As FinCEN operates at a federal level and MSBs are regulated at state level, I'm also curious whether there are any exemptions you could seek if you operated within set limits.
You were smart to seek advice in advance. I've worked for a cc provider and they'll shut down your account and make a suspicious activity report in a heartbeat if their algorithms think there's anything fishy about the account transaction patterns.