I like how the few select PS3 fanboys jump on anybody trying to bring on a logical argument as to the impracticalities of having a 400 GB Blu-Ray Disc. I mean, calm down!
If they dramatically increased the read speeds for Blu-Ray, it might be feasible for other things besides creating textures and models for games. Current methods for disc technology and game development prohibit a 'requirement' for that much space.
If and when those methods change, however, it'd be a whole new ballpark. :)
The BuShA owns all!