Thanks to a comment by Mister Matt on the board member kiss thread, I searched MMS and found this fascinating conversation.
I also have had first hand experience with this. I had a stalker once, I wasn't one.
At worst, a stalker is very frightening and at best, very annoying.
I don't think most people consider their behavior to be stalking and in most cases people are just trying to be nice or have some contact with an actor they like. You need to step back and think about it. How would you feel if a total stranger showed up at your job or school every day waiting for you? Wouldn't that feel creepy even if the person were not doing anything out of line?
When people wait at a stage door to greet and meet the actors, it's very sweet and the actors certainly appreciate the kind words and hearing how much someone enjoyed the show. Most actors I know try to return the kindness by chatting a few minutes, signing autographs and taking photos. It's a way of showing appreciation for the support of the audience. It does not mean the actor is going to become your friend, invite you to their home, give you their phone number or any other simialr gesture.
Please keep this in mind. Actors are frequently the victims of stalkers and anyone who goes overboard can make you feel jittery when you walk outside and see them for the fifth night in a row waiting specifically for you. Nothing will really come of it so, why bother? Your intentions may be good but, the actor does not know that.