Plus such a system would be a perfect instrument for implementing enforced gasoline rationing.  It would be quite easy to configure the system so that the black box allows you to drive only X miles per week and then automatically disables your car. Or if the State determines that you have been a naughty boy, it could keep your car disabled for a certain period as a form of punishment.  

When my paranoid side gets the best of me (which seems to be happening more and more these days), I sometimes wonder whether this optional LO-JAC (sp?) system that is available on some GM cars is really a Trojan horse for the government to get its foot in the door to eventually make it mandatory for all new cars to have such a black box.

There is something to be said for keeping one old car with a points-and-condenser ignititon system: i) it won't be knocked out by an electomagnetic pulse in the event of a nuclear war, and ii) it can't be disabled remotely by a third party in the way that an electronic ignition can. In addition to my daily drivers, I just happen to have such a car: a 1968 Beetle. A great car for the Sixties, and perhaps a great car for the post peak oil Road Warrior scenario (after a few serious performance modifications, of course).