Huh. This is somewhat a weird one that makes sense, sure. Microsoft has had all sorts of interesting news with the Kinect/brand new Xbox 360, but there's another extra little incentive to get the shiny black console. The Kinect, as a somewhat powerful device itself, sips away at energy. It sucks up enough juice, in fact, that users of older Xbox 360s are going to have to use a separate power adapter to make this special camera work.
Thankfully, if you have enough expendable cash that you want to buy this new Xbox SKU, you're in luck, as according to Joystiq, the new stealthy Xbox will not have this problem powering both itself and Kinect. So there you go!