Experience has taught us that if something can be abused then it will be abused.
True statement. However, one must ask if the march of technology can be stopped, especially when people enjoy using it themselves.
With cell phones in the USA, it started with a well-meaning law that required all new phones have GPS capability in them; even when turned off (so long as they had a battery in them). This was supposed to be for the purposes of 911 emergency calls; so that emergency responders could get the general idea of where to look if a person could not identify their location. Very innocuous and probably a good idea. Soon, by law, all cell phones had GPS in them as required by law. Most people didn't even know it was in the device; it was pre-smartphones.
Then the manufacturers of phones started figuring out things they could use the GPS for, and when smartphones hit, it was off to the races. Now it was a boon to consumers and a selling point for manufacturers.
Then some smart cookies at various government investigative and intelligence agencies figured out that if all cell phones had GPS devices by law, then it wasn't terribly hard to track them as if they were wearing an ankle bracelet (which is basically the same bloody thing). The question was whether or not they could do so without a warrant.
The Patriot Act made that question moot, as law enforcement could request phone records without a warrant. However, even that had limits; a special panel had to agree to allow it (they always do, it's a rubber stamp) and it's a hassle to go through the paperwork. However, some other egg-head figured out that if the government puts what is essentially their own cell phone on your car, they can certain access their own records without a warrant; after all, they are the customer.
Add to this basic premise that in the USA, a person has no legal expectation of privacy when in public. For example, if a man is cheating on his wife and a private detective takes photos of him entering and leaving his mistresses' house, he can hardly cry foul; he was seen in public and a photo is no different than a person simply seeing them enter and leave; it's just a more definite record than a memory. However, what if the government, in order to ensure that holders of top-secret clearances are not dilly-dallying with foreign spy femme fatales chooses to spy via a GPS unit stuck on the person's car? Is that an invasion of their privacy? Well, if they were being followed the 'old fashioned way' by a cop in a car with a camera and a radio, it would just be routine police work. So is this any different?
Any of us can be legally surveilled by the police at any time, for nearly any reason, without a warrant. I'm not talking about wiretaps or that sort of thing, but just the old basic techniques of following a person about, watching where they go and with whom they meet, digging through their trash, etc. Is sticking a GPS unit to the bottom of their car essentially different? It's more precise and more cheaply and easily done, but is it doing anything that can't be done now legally by other means? I'm not saying I like it or agree with it, but breaking it down to basics, I'm not sure it is fundamentally different from routine and legal police work.
For the most part, Big Brother is not interested in or capable of tracking every citizen, either by smart phone or GPS planted on a car. It's simply a sea of data that no one would have any interest in mining, for the most part. Even for scientists interested in data mining of the mass information, it's less about you or me than it is about groups and demographics.
Consider this; since cable television companies went to 'on demand' and digital delivery, they know exactly what you are watching, when, and in what room of your house. There is no more need for Nielsen ratings, they know precisely who is watching what when. That is far more personal data in many ways than where we might be driving on any given day. The credit card companies know precisely what you buy at the grocery store if you pay with credit or debit card, and the stores know if you use a shopping affinity card for a discount! Tell me that's not deeply personal information! Do the law enforcement authorities also have access to this information, with or without a warrant? Good question, I don't know! Has anyone asked to find out?
As a person in the IT field (as you are, and by the way, I've been involved with SCADA by brushing up against it and I'm reading with interest the story about the SCADA system hacked recently), we know that too much data is as useless as too little. We also know that when you know from whence the data comes, you can also manipulate the decisions people make by manipulating the data they are fed. If a GPS unit on my car ended up on a train headed for Vermont, I'd find that rather amusing. If my shopper affinity card was given to a homeless person who buys lots of booze in a bad part of town, that's amusing too. If my cable TV box is moved from one room to another without the cable company knowing, and left to watch the cartoon network 24/7 with no TV actually hooked up to it, that's another.
I'm trying to say that I'm a bit less concerned that I'm being watched than I am that I know about it. If I know about it, I can take steps if I so desire. Culture-jamming is fun.