Today is official ‘app monetization day’ it appears. The original Microsoft Ads SDK only supported Silverlight if you recall. And as of today it supports XNA (high end games) as well.
It’s still US only but this opens the door to more apps that developers can monetize (you know, release for free and get some ad revenue). OK, make this thing global and you’re in business Microsoft.
More info can be found here. Thanks for the tip Sleepy Daddy!