The rule that no person shall make more than three Facebook moves in one night. This includes status updates, comments, likes, and sharing links. A preventative measure from being one of those annoying people who doesn't shut up on Facebook.
Guy 1 - "Dude, like my status."
Guy 2 - "Sorry bro! I already commented on a status, shared a link, and liked another status. Anymore Facebook moves will make me seem annoying and addicted!"
Guy 1 - "Damn Facebook Limit Rule."