Someone on Facebook, Myspace, or any site of the sort who:
A) Accepts random friend invitations from most anyone.
B) Invites as many people as possible to become their friend, (particularly if they have friends in common) whether they know them or not.
Friend whores are usually teenage girls, but really anyone can be a friend whore.
Most friend whores are considered to be "social" in real life as well.
"Yeah she has 1000 friends on Facebook."
"She's such a friend whore