[citation][nom]back_by_demand[/nom]Tracking by RFID tabs from 40m?How about tracking by number plate recognition cameras from a lot, lot further away.[/citation]
Yep, plus no matter how directional your RFID scanner is, the camera can actually pinpoint your location, while the RFID can only get you a general area. Not to mention with a camera you can, well, record faces and such...
Also, tracking by RFID-like tags has been in use for about two decades in Portugal, for toll payments. You pass under an archway, your tag gets read (you have to buy one, btw), then at the end of the month the company automatically gets the money from your bank account. Simple, and can save A LOT of time, especially in high-traffic tolls. In recent years, this system has even been extended to a few underground parking spaces and gas stations. Can't see a problem with it, you can't know where *I* am, you can only know where *my car* is, and I'm not the only one driving it...
In more relevant matters, I do think this might become a problem in the future. However, it can be more or less controllable: you just need to completely separate some parts of the car electronics from the rest.
Let's face it: apart from very limited interventions at a garage, there is, nor should there be, any reasons for having security features (and the central CPU) of a car communicating with anything else, thus shouldn't even be allowed access to an external network (preferably, only the power source should be shared, if really needed).
At the same time, entertainment appliances and GPS have NO need to be sharing information with, well, anything under the bonnet, really. They might need to interface with an external network and with users, but that's it. And, if something gets corrupted/catches a virus/whatever, it won't compromise the fundamental security features.
It seems to me it's mostly a design problem, really. Sure, you might need to firewall your car (which anyone with a carputer accessing external networks already does, or should do, anyway), or even run AV software, but provided you keep security features and entertainment/location features unable to share data between them, you should be fine.
Cheers.
Miguel