Someone that tries to add all of your friends on your MySpace/Facebook friends after you add them on your friends list.
After I added Candace to my friends list, she added a bunch of people from my friends list, so now we have a bunch of mutual friends. She's a friend stalker.
A friend who is obsessed with you and won't stop calling, following, and trying to be seen with you.
Ellen is such a friend stalker, she won't stop calling me! I don't even like her!