Are dedicated servers required for multiplayer games?
No, a dedicated server is not required though it will provide the best gameplay. D3 allows games to be hosted so that for small games a player may start (host) a game. It is always best in this case to have the player with the best connection (most bandwidth) host the game. Also see the section [5.14] referring to lag and loss and section [6] referring to setting up dedicated servers.
