I recently tried a product called AdWhirl from AdMob. AdWhirl is an open source ad aggregation tool. Basically you put an AdWhirl ad in your application, it will query the various ad agencies and try to find the best ad to place on your page. In other words, you could run ads AdMob, Quartro, iAd, your own ad network, etc. The idea is excellent.
The setup is not for the faint of heart. AdMob will let you use their server, but you should really setup your own AdWhirl server so you are in control. You will also need to register directly with each and every ad network you will be using. Registration can take weeks, so you should do it as soon as possible. On the application side, you will need to include the library (jar) for each platform, which can make for some large applications. After that there is some minor configuration, but nothing too bad.
I really like the idea, but this implementation isn’t for me. When there is an update to the ad network libraries you have to update your application. I would have liked it better if the jars were loaded on the server, so the clients didn’t have to talk directly with each and every client. I also don’t like having to run the service on my own server, for busy applications, it might eat up a signficant part of the savings.
The absolute worst part is getting paid by multipal ad networks! In the industry you have Net-5, Net-30, Net-60, Net-90. Its really had to stay on top of. A check can eaisly go missing and you would never know it.
When would I use AdWhirl? If I had an application that generated a lot of views (inventory). I might want to sell my own inventory, AdWhirl would allow me to sell a portion of my inventory, and still use a network for the remaining. Excessive inventory is a huge problem publishers, and AdWhirl is a good solution for it.