After getting (presumably) millions of users taking advantage of their great (free) ad serving service, Google have now made it only work with their products. I expect most medium-sized sites will just accept this and start paying Google a percentage of their income, because it is more convenient than setting up an alternative solution....
The email from Google reads, in part:
Starting September 5th, 2012, the new version of Ad Planner will be dedicated to supporting research on placements on the Google Display Network, which comprises more than 2 million sites from across the web.
What does this change mean for you?
You can no longer research domains or ad placements that are not part of the Google Display Network.
Publisher Center, the feature that allows publishers to claim their own sites, list relevant ad placement availability & pricing, will be deprecated
Imagine if Microsoft told customers that you need to pay $5 to receive future security updates?
Imagine if Toyota stopped making cars and doubled the price of spare parts?
Are you sure you're thinking of the right thing? The Ad Planner is a tool that AdWords advertisers use to find ad placements. The publisher portion was where you could list your sites so advertisers could target you.
The DoubleClick for Publishers (previously called Ad Manager) is the ad serving tool, and as far as I know, that's still working the way it always has.