A multiplayer inclusion to Fable 2 would totally blow me away. Can just imagine going on quests with you guys. Would be cool having a Project Ego.net Arena tournament too.
You could run your own shops, have an evil, good, or neutral faction, and even marry a player online (though it would be creepy if it was a guy playing the gal in the game *shudders*)
I don't think Albion is large enough for 10's of thousands of players all roaming around. Morrowind is large enough for online play, but nooooo, they wan't offline...