Never ever.

This is one of them.

Plus, I'll bet they didn't engage the emergency brake. Owners of automatics try to convince me that putting it in Park is good enough. No, it's not. I can think of more than one time a car in Park slipped away and people inside were killed.

This is among the reasons I drive a stick.

Every gas station I've seen has a sign informing the customer that the engine must be turned off at the gas pump.

Also, if you don't leave the car running keeps a car thief from hopping in and taking the car.