Quite simply, the main feature Microsoft has been touting to advertisers is the ability to detect who is in the room and target ads accordingly. The gold mine is not in Kinect for games, its for the TV/Video/Music/Netflix/Hulu consumption and the "big data" of being to tell that there is a 30-35 white male (recognized and tracked via Bing), 30-35 white female (Not logged in but we know her profile), and another 25-30 female guest that we have an 90% confidence is person Y who has a bing account. Lets target Ad X, Y and not Z.
MS will put Nielsen to shame with all that mineable data. There will be still be people who leave the MS eye on all the time, at least now you have the option to unplug it.