I think that it's going to become an issue, not when the police are shooting the GPS trackers at criminals, which is perfectly fine by me, but when car makers start giving discounts for cars with pre-installed gps trackers that are outside of the consumers control and ability to turn off.
My understanding and I could be wrong is that Onstar or the Microsoft Sync program can track you even if you are not a paying subscriber to their service. With a proper warrant the police could have Onstar locate your vehicle and it wouldn't be a stretch that they could switch the vehicle off if asked during a chase. You also have the Event Data Recorder that records what your car is doing at any given time as well, that data is stored in a database somewhere, our chevy can even text us when it wants a fricking oil change or the tires are low, but that could be part of the Onstar service.