Every time a car alarm mine has gone off, it's been a false alarm. Every time I've heard a car alarm, and been able to determine (or unable to avoid determining!) which car was making the noise, it's been a false alarm. Next time I buy a car, I'm absolutely making them show me only cars in which I can disable the alarm, and where they'll show me how. (The salesman lied to me about this one having an alarm. What I get for believing a salesman. (Well, and for giving away what answer I wanted.))
Car alarms have been the butt of jokes pretty much as long as they've been common. They're so useless — and have always been so useless — that I find myself wondering if they weren't a necessary prerequisite to the TSA. If Americans hadn't grown used, over the preceding 20 years, to the most conspicuous example of "security" in their lives being something that generated a lot of inconvenience for no good purpose, would we ever have accepted the TSA?