Powdork - 7:07 am on Apr 14, 2005 (gmt 0)
It occurs to me that Google could check this by alternating ads on the page. Pages that have a CTR that fluctuates noticeably with changes in ads could be said to be AdSensitive whereas pages whose CTR does not fluctuate with changes in ads could be said to be AdinSensitive. Clicks from pages with higher AdinSensitivity could be said to have less relevance since people click at the same rate regardless of the ads shown.
I have no reason to believe Google does this, but it is very scalable and it is determined by changing variables completely within their control. So it seems like a good idea.