Everyone @ MS thought it a good idea. Especially when they saw how much the advertisers are going to pay them. And all that advertising is curtailed to you so you know what that means.....
It's curtailed to us? What does that mean?
Rather than 'generalized' advertising, the ads you see are curtailed i.e. narrowed down to just you - personalized for you by tracking your every move. Then the smart guys take that data and based on what you look at, read, listen to and what sites you go to or have been to - narrow down the advertising to what they think will interest you and what you will buy. And just like the NSA was collecting our info, all users here have already agreed to allow this. It's in the fine print of the user agreement that nobody ever reads.