THIS is SO COMPLETELY wrong. I don't know where people come up with information like this, porkchop. In a public place, or on private property that you have a right to be on, you can ABSOLUTELY follow someone. You think you recognize someone who stole your car and you want to see what car they are going to. You think you recognize someone you went to high school with and want to get a better look. You think you just saw someone steal a dog, and you follow them all the way across town to see if that's true.
YOU CAN ABSOLUTELY follow someone if you want to. With friendly or hostile intentions, providing those intentions are based on legal reasons, i.e., trying to make sure you know where someone is when the cops finally arrive to check them out.
You can even "stalk" someone for romantic purposes until the victim asks for help from LE and is able to get a restraining order, which isn't always that easy if someone is just following you around trying to interact with you. They have to do more than follow - they have to actually THREATEN you. They can't just want to be in your presence.