Hear that? That's the sound of coins hitting the mental floor at a breakneck pace, and if PayPal's meteoric success is any indication of how it'll do in mobile well, stockholders should be pleased. Nearly three years after first hearing of Jack Dorsey's Square (formerly 'Squirrel') project, the most hated division of eBay is coming out with a rival. President and CEO of eBay John Donahoe took the wraps off of the device at Ghirardelli Square in San Francisco today, with an aim to bring PayPal to "mercha