Looks like Google recently changed their terms of service. They aren't allowing revenue sharing on forums anymore. Quote from Webmaster World. "In addition, You agree that while You may display more than one (1) Ad Unit on each Site Web page, You shall not display any Ad Unit on a page that contains Ads associated with another Google AdSense customer (e.g., Your Web hosting company), unless authorized to do so by Google or such other AdSense customer, if authorized. So what does this mean? It means that "revenue sharing" AdSense sites are now against the terms, as would be displaying your own AdSense on a site where the hosting company is already showing their own AdSense (ie. such as a Tripod site). "Revenue sharing" is especially popular on forums, where the originating poster can have his/her AdSense displayed on the thread a certain percentage of the time. Now, you can only do this if you have received specific permission from Google AdSense to do so, otherwise, you will be violating the AdSense terms. I clarified this with Google, as well, as I wanted to make sure I understood this correctly.
I don't believe you are reading that correctly, say for example this site. We will still have our ads displayed at random because we fall in the category of "such other AdSense customer, if authorized"
See this thread where Shawn commented on this issue. http://forums.digitalpoint.com/showthread.php?t=11464&highlight=twilight+zone
The way I see what that is saying is that you can't have multiple publisher IDs on the same page view unlses authorized by Google or the publisher themselves, "if authorized".
Yes that's right, you see different adsense ads on this page but never two at once and that's what is not allowed which is good!
Funny, I asked about showing two ads from two publisherID's on the same page at the same time. It was in relation to me providing development and hosting in exchange for revenue. At the time they said it was fine. I wonder if that qualify's as "authorized". The quote also does not make it clear if it is ok to rotate through publisherID's. Only showing one at a time on an alternating basis. Each page impression is a new or different page right? I guess I'll follow up with them when I'm ready.