The best example of this is m-pesa by Kenya's Safaricom. In Kenya the banks market share has been totally cannibalized because most people couldn't afford a bank and then when most of the population went to strictly m-pesa so did a majority of the vendors, etc. I wouldn't say bitCoin doesn't have a shot at replacing that, but it's got a long long way to go. http://en.wikipedia.org/wiki/M-Pesa