Great post! Overkill perhaps, but Google has been known to go overkill with a lot of other things (so many babies thrown out with the water ). With the amount they stand to earn from each Publisher (thousands from each successful AdSense publisher), setting up extremely detailed tracking on an Ad/Niche/Keyword basis wouldn't really be out of their reach. It'd feed their desire for relevancy, it'd give them massive amounts of data on how well a site performs and they wouldn't be losing out when one of our sites smart prices our entire account! Although it's entirely possible their current infrastructure might not support such a massive amount of processing. Food for thought on the future of Google, perhaps?
I have a couple of forums, one has 53k members and the other is 35k. The larger one does pretty good with adsense but the other does not so I've been running YPN on it (it still doesn't do that well there either). The other day I put the smaller site back on google to try it out and entire earnings went down about 45% for the day. And, it's taking a few days for it to come back up after taking the smaller forum back off.