“According to the letter, miners are still free to purchase goods or trade with exchanges with the bitcoins they produce whether operating as individuals or businesses. The news should come as a relief for smaller-scale mining operations. Jerry Brito, senior research fellow at the Mercatus Center, indicated that FinCEN wrotein a private letter last July that all miners would have to register as MSBs, and uncertainty had remained since then. This could have put many individuals out of the mining business with its range of compliance regulations, such as having an auditor on staff. The exact wording of the letter still leaves some room for interpretation, though.”
http://www.coindesk.com/fincen-bitcoin-miners-need-not-register-money-transmitters/