The Reputation System is a simple way of preventing people leaving rooms.
The system has 3 stages, when you create a new account you start off at 'Laughing Smiley' but for the purposes of an explanation I'll call it 'Rep +1'. At Rep +1 you get Gold and Experience bonuses at the end of a match.
If you leave a match, you will drop to 'Neutral Smiley' or 'Rep 0'. At Rep 0 you don't get any bonuses, playing 2 matches without leaving will restore your reputation.
If you leave again, you will drop to 'Angry Smiley' or 'Rep -1'. At Rep -1 you can be kicked from matching games from any player in the room. This makes it difficult to get a match. Playing 4 matches without leaving will bring you back to Rep +1.