http://www.1up.com/do/newsStory?cId=3161942
*shakes head*
The requirement is primarily linked to hard drive limitations. "It's the consequence of having a limited size hard drive, with a lot of other things to fill it out," he says. Companies are allowed to expand the required size, but the game should always run on the original requirement -- users have to approve the change. If the requirement goes up, Microsoft is playing with the idea of allowing the ability to degrade -- those are Microsoft's words -- the experience. Their ideas, straight from their presentation:
Lo-res models/textures
Place certain areas off-limits
Stream assests from server (slower loading)
*shakes head*