License plate scanners could track religious practices, political activities, and affairs
There are some uses of automatic license-plate readers that most people would agree are relatively unobjectionable — looking for cars that fled crime scenes or have been stolen, for example. The real problem is that when the government stores that information, it is not trying to solve an ongoing crime — it is building a database. These databases can quickly fill up with all sorts of details about how people lead their lives. By piecing together the locations of a particular license plate over time, the government may be able to determine if someone goes to church, synagogue or mosque regularly; whether they go to meetings of a particular political group; whether they participate in protests; or even if they are having an affair.