A few years ago there was someone at a kiosk in a mall in NYC (I think), who got busted skimming. She was double-swiping, once through their POS system, and then a second time on a Palm Pilot with a magnetic stripe reader attached. She got busted because someone saw her doing it and got suspicious. Now, think about the number of times you hand over your card and it leaves your line of sight to be swiped. Other than retail stores, it happens to me all the time.