I've watched this documentary by Vice about Gang Stalking and it's a very good doc, but it just seems it's paranoid people who think they're always being followed?
That makes more sense and if they begin with stalking it can probably become dangerous later on.The short answer is yes
The longer answer is, that most people aren't going to experience it. Those who do, tend to have something at the core of it. For example, people looking into cults like Scientology often end up being stalked by the cult. Someone famous might experience it at some point in their career. In most cases for the average person, it's a delusion and most likely linked to a mental disorder.