White-hot payment processing startup Square continues growing at an eye-opening rate. Only 2...

White-hot payment processing startup Square continues growing at an eye-opening rate. Only 2 months after stating it's on track to do $1B/year in transactions, Square now says it's on a $2B/year pace. Square's runaway success could get in the way of Google (NASDAQ:GOOG) and eBay's (NASDAQ:EBAY) mobile payments ambitions (I, II). (previously)