Microsoft has made Avatars available to user-created games on 360, and that permission comes with some guidelines. Found the last rule on this page interesting:
http://creators.xna.com/en-GB/article/avataruse
I assume it's to stop pervs like us from putting huge boobs on the female Avatars. :)
Well, that sucks. I guess they just don't want to get too involved with the consequences.
Now THIS is love!