The expose on 60 minutes a few years ago on gas station scams was enough to scare the hell out of me. Guys were using razor blade rings to cut fan belts and puncturing tires on the sidewalls so they couldn't be fixed easily in order to sell new ones. Some places were selling hundeds of belts and tires a month.
The message I got from the scams was to almost never allow anyone you don't know to get close to your car, and even if you know them watch closely.
