If you put an ad rotation script on and displayed them once at at time and not at the same time, that would be as close as you could get.
Actually, you're both mistaken. With the updated TOS from this past February, they changed it so you CAN show ads from various AdSense accounts on the same page, as long as you don't exceed the total number of allowed ads per page. To make sure, I e-mailed my rep and asked specifically about this. Here is what she said: It sure makes it easier when doing revenue sharing on a site!
Actually, the key is what it doesn't show any more. The following line was removed in their TOS update: Here is a page that discusses all of the changes from that update: http://www.jensense.com/2008/02/26/tracked-with-web-beacons-by-adsense/ I've already posted what Google told me directly. It seems quite clear.
Yes, you can. Not on the same ad unit of course, but you can have two different ads with different pub-ids on the same page.
Two pub ids in a single ad obviously won't work, but two different pub ids on a page isn't a problem.
it works, but no matter how much id you have? basic rule for adsense is 3 ad per content, referral and link ad.