It seems like you can now request to join the pilot Microsoft ContentAds program as a publisher. Currently, there was really no public method to request to show Microsoft ContentAds, via the adCenter content network, on your site. But now, there appears to be a form at http://advertising.microsoft.com/publisher that you can sign up at.

By completing the form, you have a chance at:

To keep informed about new developmentsReceive invitations to participate in focus groups or feedback sessionsAnd most importantly, possibly be considered for participation in an upcoming pilot program

So does this mean that Microsoft will soon be opening up their publisher program and be competing directly with Google AdSense and Yahoo Publisher Network? If Microsoft opens up the program soon, they can likely take away publishers from Yahoo. Yahoo is still closed to non-US based publishers.

Forum discussion at DigitalPoint Forums.