It looks like Microsoft is already experimenting with their own advertising solution similar to Google Adsense. The buzz is out and Microsoft is currently naming their solution “Microsoft Content Ads”.
As with Google business model, advertisers join Google Adwords to buy advertisements which are then serve onto publishers sites who has chosen to join the Google Adsense network. In Microsoft’s case, it would be buying ads in Microsoft Adcenter and ads will be displayed on publisher’s site who joined Microsoft Content Ads.
Microsoft Content Ads is currently still in limited beta testing. You can however opt in to join the program by filling in this form.