I was once in the short term carpark of Perth Airport, returning to my car after picking some friends up. As I got closer to my car I got out the keys and pushed the boot release button. The car immediately alongside me opened it's boot (trunk for the Americans) as did mine three cars down!. The car was the same make as mine but a different model. Being mischievous I decided to check out if this was just a fluke, but it wasn't! I could open and lock all the doors and the boot as if it was my own car.
I was tempted to see if I could start it as well, but although my key fitted the ignition lock, I chickened out and didn't try to start it. I simply closed everything up and relocked it all.
Obviously there are not an
infinite number of remote locking codes!