For high end cars, I wonder how many are vulnerable via their OBD ports? I bet a few go through a car grooming service on a regular basis where someone just needs to enrol a new key/fob, and then just wait 6 months or so.
Delete cookies?! Are you insane?!
resurrect: A factory immobiliser with a timer is a great way to help decrease chances.
and well for alot of cars you can just get a wire from the battery to the starter solenoid to bypass the ignition all together. (although the starter motor will be constantly on)