Halo 3 to feature Four-Player Co-Op?
"The game cannot start because all players are set to observer. Too many players for splitscreen. Only 2 players may play splitscreen coop on the same Xbox 360 console. The party size is too large to start the game. Up to 4 players may play coop on Xbox Live or System Link. Loading information from Xbox Live..."
So there you have it, straight from the code...
Thanks to CVG for the info....