According to friends who worked in gas stations this is more common than you'd think. Usually when people went inside to pay. The nozzles are apparently made to break away and it automatically shuts the gas off. The bad news for those guys is that gas stations also have cameras pointed to catch the liscense plates, and people who drive off with the nozzle get a bill for the replacement cost.
I was going to post last night and say almost exactly what Lise said. The only difference I'd make is that not all stations have cameras at the pumps, and at the ones that do, it sometimes isn't clear enough to read a license plate. You try to have a camera cover two different pumps. The best I've seen is a camera that moves back and forth between pumps and zooms in on the place where they expect the license plate to be. Doesn't always happen that way, because of many different variables. Plus, some states don't require a front license plate, so you'd have a 50/50 chance of having the camera coming from the wrong side anyway.