You should know that being a money transmitter is an exceptionally risky and time-intensive business to be in even if one is not "categorized as" a money transmitter. Even if the government ignores you, criminals will not. You are currently betting that your fraud prevention expertise is better than every criminal's fraud execution expertise. You will likely not win that bet. Do you understand that your adversary here has twenty people who are smarter than you and have years of experience on his payroll? I am not exaggerating in the slightest. Breaking your system wide open will not be his side project. It is his core line of business. You will just be a juicy target of opportunity, to the extent that you have worthwhile volumes. Note that four figures is already worthwhile.
As for the regulatory side of things, I'll pull you the exact citations when I get back from (ironically) a coffee run.
Re: fraud I've definitely been disillusioned that I can handle the tide myself, but OTOH I imagine fraud prevention is a lot like security- make sure the wall is higher than the water. I'll just have to figure out how to do that in a way that's safe, economical, and keeps the core idea behind the service working. It will almost certainly involve hiring people, or cutting off the influx of business down to- say- 5 cards a day.
[(5) Money transmitter (i) In general. (A) A person that provides money transmission services. The term “money transmission services” means the acceptance of currency, funds, or other value that substitutes for currency from one person and the transmission of currency, funds, or other value that substitutes for currency to another location or person by any means. “Any means” includes, but is not limited to, through a financial agency or institution; a Federal Reserve Bank or other facility of one or more Federal Reserve Banks, the Board of Governors of the Federal Reserve System, or both; an electronic funds transfer network; or an informal value transfer system; or
(B) Any other person engaged in the transfer of funds.]
You unambiguously accept other value which substitutes for currency from one person. You equally unambiguously transfer value to another location or person, under multiple legal theories: a) the Starbucks card is one location, the Bitcoin account is another, b) the person holding the card and the bitcoin account may be different parties, c) your business operates as a transport layer between your customers and the company which you are unloading thousands of dollars of Starbucks cards on, and as those are different persons, that means you are transmitting that value.
You might think "But wait, FinCEN narrowed the regulations a bit for 'sellers of prepaid access' specifically to avoid overburdening them." Great news for Starbucks, bad news for you. You are not a seller of prepaid access, which you can verify by reading pg 45403 on of the Federal Register.
You are, instead, using Starbucks cards and Bitcoins as a transport layer for value. The government is astoundingly non-neutral about that choice of business.
It's not about transferring value - it's about substituting currency-equivalent value. What's the substitution going on in a mining pool? (And don't say electricity for coin, electricity is not valued similarly to a currency. Similarly 'claim on mining output'.)
The currency equivalent value is securing the chain of BTC transactions and discovering new blocks, making the system work at all. New blocks have a currency equivalent value and doing transactions has a currency equivalent value too.
Patio11 only posted an excerpt of the rules. Most businesses which fit this excerpt are excluded by portions of the rules not posted here but which are contained in the link. For example, those exceptions are why retailers who sell gift cards are not treated as money transmitters.
As for the regulatory side of things, I'll pull you the exact citations when I get back from (ironically) a coffee run.