I think it's a great idea and inevitable, just like seperate, if not external power supplies for GFX cards.
It probably needs Nvidia to pioneer it, so people wont criticize it so much because it's Nvidia, but it'll def come.
Hmm, I have questions about this though..I'm envisioning a shuttle style SFF for your vide card someday. In some way this actually makes things simpler for the laymen. It's a modular component now and you dont even have to crack open your case. It also open up a lot of cooling options. However, having two boxes for your PC instead of one isn't very elegant.
But mainly, how would this connect to your PC? In the shuttle SFF scenario, you'd likely need to set it on top of your tower (or at least behind) which would presumably require some USB style cable..would this cause severe latency issues due to the length of the cord?