Having information about someone is fine. It's not stalking nor harassment when you're privy to their location, where they live and work, everyone they interact with, their conversation, every newspaper and article they read, and every purchase they make. But it's creepy especially if this information is collected surreptitiously. Why collect this information in the first place?
It becomes harassment when this information is used to target someone. It is stalking if this information is used to follow you around. It is literally "cyberstalking" when it does. If someone is tracking you, they are stalking you.
Every website owner who puts code from Google or Facebook is complicit in this tracking/stalking.
When everywhere you go banners are being put in your face with messages tailored prod your fears based on what is known about you. When psychological tests are carried out en-masse [0], this is harassment.
