[viraptor]

This has happened in google image labeler. Now offline, it was a game where two random people were matched and needed to find new tags for the same image - the scoring was cooperative so points were given when you both chose the same word in the same game. /b/ of course quickly organised the jesusporn metagame... Label the first image as jesus, second as porn, third with jesus, etc. This resulted highest scores for some time.