I don't know about paranoid people or the extremes this article speaks about. But group stalking is a thing,usually with an end goal but also for some sick psychological satisfaction.

It's much like how they get a person (usually a female) to install a remote access trojan and basically mess with them and share videos,webcam recordings,etc... On forums (pretty sick stufd,they call the victims their "slaves"). Haven't confirmed it first hand but I can see people coordinating cyberstalking. But in person stalking takes too much resource for me to believe it's done for the sole reason of just messing with someone.