Has it been specified that it will require a constant internet connection or not? Starcraft 2 requires you to authenticate with a valid battle.net account to play the single player mode, but it doesn't require you to be constantly connected to the internet to play. If it's different for Diablo 3, I would suspect they are just requiring everyone to play on battle.net which would seem pretty lame to me. I see no problem with allowing people to play on a LAN with friends or single player without an internet connection, if authentication is required regardless. The claim I've heard regarding their motives is that they are doing this to prevent piracy.