Someone who posts on their girlfriend/boyfriend's wall to express their love in an inappropriate, sickly way, knowing full well that the message will appear on all of their mutual friends' news feeds.
Maybe for attention, maybe to make everyone feel bad because they are obviously the ultimate couple, but one thing is for certain; the world would be a better place if they just IM'd the damn message.
Can also be applied to close friends of the same gender who enjoy gaying each other up in public, despite being straight.
Guy #1: Damn, Steve, stop commenting on yo' girl's Facebook wall! She's gonna think you're clingy.
Guy #2: Plus you're annoying pretty much everyone who knows you both. Get a room and stop being such a Facebook exhibitionist.
Steve: WHY MUST YOU TRAMPLE ALL OVER OUR LOVE?!