This could happen in chat rooms, and other parts of the net. That said, online chat's are great when structured and kept on a theme that isn't too personal, or between friends in real life who moved too far away from each other. I'm sure every celebrity has heard about this phenomenon. On the internet it's closely linked with harassment, sometimes that's what it is, sometimes it's just another way of stalking a victim. The interesting part is that it isn't limited to celebrities.
Stalkers are often relatively indiscriminate.
Also, it doesn't show. Their family may know something's off, but you're unlikely to know. In fact, don't trust anyone, even if they say they're a celebrity. Too easy to cloak your identity on the net. My name is Annie.