Not a quandary for the ages, but...

When a radio station's patrol team awards cash to those driving cars with the station's bumper sticker, should those drivers also have to be listening to the station when the patrol team spots them?  Ostensibly, the purpose of a bumper sticker is to say, "I listen to this radio station," but driving around with the sticker on your car might influence others who wouldn't have listened otherwise to tune in.