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.
I think you mean "targeted." You should look up "curtail" and find out what it means.