I read this interesting blog thing, and she has the Idea of player housing in WoW. I think it would fit in nicely, although her system of Tier 1 (Small), Tier 2, and Tier 3 Houses are kind of... it makes everyones house the same. I would want a type where you added rooms.
I know, this is the Blockland forums, but I just wanted to discuss it.
http://druidteam.blogspot.com/2009/01/player-housing-intro.html The reason I want this, is that it would add another part to the endgame. In WoW, theres raiding and PvP. That can get a little dry after a while. I wouldn't mind if it was expensive as hell, but it would add more feeling on involvent.
Pros -
Moar Endgame
Fun
Customability
Cons-
May be hard to store data. The data could be as simple as possible with the layout for peoples houses being like forge saves in halo 3, they are only 100 - kilobytes.
Only a few terabytes on their servers.
Again, I know this is the BL forums. This game is so popular its taking over.