The Kinect has a user base of 18 million units world wide, let's assume only half of those are USB units, that's 9 million units. Instead of Microsoft allowing home users to use their XBox Kinect with Windows Metro apps, home users will be forced to buy a new Kinect to use it with Windows apps (commercial apps anyways, they can use apps made with the beta SDK).
With this move Microsoft has reduced the PC user base of Kinect to 0, eliminating a huge audience for developers. The reason given was that the XBox Kinect was subsidized by game sales, but if using that defence, why not just subsidize this Kinect through the new app store Windows 8 will have? This would let home users use their existing Kinect and keep Microsoft's bottom line doing well in the long term. This is just a very dumb move overall.
Foreword to pro-M$ trolls, I did RTFA and I know about the "near" feature of this new Kinect, but it still doesn't justify this move.