facebook popper
A Facebook popper is a person who logs on just to check who's online and then instantly logs off like they're being chased by a bunch of angry raccoons.
I logged on, saw my boss was online, and popped off like I was hiding from a monster.
He saw no one he liked and logged off like he just lost a bet.
She logged on, saw her crush was online, and popped off like she was running from a zombie.