Bitcoin got a major new ally this week, as Overstock.com began accepting the alternate currency system as payment. Overstock isnt the first company to accept the currency, but its larger and more powerful than previous companies like Reddit and OKCupid. Bitcoin has come under fire from economists who see it as unstable on principle, but the move carries little risk for Overstock, which will presumably continue to do the majority of its business in more conventional currencies. The bigger uncertainty comes from Coinbase, the bitcoin payment processor thats powering Overstocks latest move, but has never worked with a business of this magnitude.