Facehooker

A person who continuously adds 'friends' to their friends list on Facebook, though many-or-most are actually strangers or simply casual acquaintances, solely for the purpose of appearing popular on Facebook: Facehooker
Note: This person's SOLE interaction with his/her new, so-called 'friends' is: "Thanks for the add."

"I received an FB friend request today from a chic I've never met. She apparently wants to 'know' me, wants me to be number 820!?! What a Facehooker!"