numnum - 8:14 pm on Nov 20, 2011 (gmt 0)
I suppose this a naive question, but under the CPM model what is the publisher's incentive to place the ad block in a highly visible position, when all that matters is the number of page impressions? Why not just put the ad in the page footer rather than above fold? My best guess is that the amount that advertisers are willing to bid on ads appearing at your site depends in part on the click-through and conversion rates. But even this doesn't entirely make sense to me.