When you inadvertently get a "like" on facebook from someone you don't know, usually on the wall of a mutual friend. Upon further examination you realize the only reason you received a like from this stranger is because you were part of a straight like being performed on your friend's wall by the mutual friend.
Nicole: I got a facebook like on a "happy birthday" I posted on Nate's wall from a complete stranger.
Rishi: Did you see if he liked any other status's on their wall?
Nicole: Let me see... Yeah, he actually liked everything, even FarmVille information.
Rishi: Don't worry, you were just an innocent likestander.