face collector

A person that adds people on Facebook, or other social websites, in order to seem popular. They might not necessarily be good friends with them, or even know them that well, but they add them anyway to give others the impression that they're popular.

Bob: Did you see how many friends Dave has on Facebook? He must be a pretty cool guy.

Billy: No, he's just a face collector. He just adds a lot of friends to make himself look popular.