FB Stalker

Someone who hides the fact that they are online and spends lots of time on Facebook in others business: reading status updates, looking at pictures and following conversations and comments with others. He/She may spend hours looking up people from his/her past and or others friends, gathering as much information about them as possible somewhat secretively, without commenting or messaging or otherwise adding that person as a friend.

How do you know about XXXXX?
I was a FB Stalker the last couple days.
Also: FB stalking.