Bitcoin fees for users are low. But they are in effect subsidized by speculative buyers. If prices fall, Mr Swanson warns that fees will rise, making it less competitive versus traditional payment methods. He estimates that the true cost of each bitcoin transaction is $15-$20. Meanwhile, a growing number of bitcoin intermediaries are moving to work within the established financial market. Coinbase, the San Francisco-based start-up that lets people store, send and accept payment in bitcoins, has launched its own US dollar wallet service and broke records in January when it raised $75m from investors including the New York Stock Exchange and several banks.

http://www.ft.com/intl/cms/s/2/f5937b80-7ee8-11e4-b83e-00144feabdc0.html#slide1