BNet Servers are live at May 15th 12AM PDT, but installers are working now!+Mike Evans
Diablo is the series that Dungeon Siege was born from. Diablo from Blizzard Entertainment may have been the original Isometric, Fantasy Themed, Multiplayer, Hack'n'slash.
D3 is linked via the Battle Net system and allows up to (I believe) 4 players simultaneously. The Auction house was kind of an after thought that they threw in there toward the end of the design period, but Theoretically everyone who plays this game can be a Gold Farmer >.<.