BTC isn't a currency in US. I'm kind of curious where SEC draws the line, if any, when somebody sells some interest in some virtual artifact - say a website or a Farmville plot of land - in exchange for some other virtual artifact - say BTC or ISK.
The SEC doesn't get involved in Farmville plots of land, any more than it gets involved in physical real estate. It's not involved if I sell you a gold coin or rare stamp, even if you hope to resell at a profit.
Cryptocurrencies seem more analogous to these things, rather than equities, debts, profit-sharing agreements, or anything else in the SEC's official definition of a security:
But in any case, lots of Bitcoin companies successfully navigate money-transmission laws already.