Never had a problem with joy rides on 335i, e92 m3, m4, e60/f10 m5's
Occasional horror stories about a new employees or some porter taking it out and beating on it...
But thats why I went higher on the car scales
GT-R only an authorized GTR tech is allowed on the vehicle.
My R8 only the service manager and my SA are allowed in the vehicle, when I chat with the porters when I'm doing small maintenance they always tell me they ask if they can pull the car around and they are told no.