Smartpricing is NOT based upon one particular advertiser, and it does NOT happen just for the clicks from one particular advertiser. Smartpricing happens across your entire account, not just one site, but all your sites (this from Google) Why then would my filtering of MFA's all of a sudden jump my ePC right back up to decent earnings? I seriously doubt that I engaged my filter at the exact same moment that smartpricing was lifted, and I certainly wouldn't have managed to do it at the same time repeatedly.
fluid: "Ad rank for the content network For a keyword-targeted ad's position on a content page, our system considers three things: The ad group's CPC bid or, if content bids are enabled, its content bid. The ad's past performance on this and similar sites. The relevance of the ad's landing page." http://adwords.google.com/support/bin/answer.py?answer=6111&ctx=en:search&query=ctr&topic=0&type=f "Ad Rank explained! Quality Score takes into account factors such as an ad's relevancy and click-through rate (CTR) (i.e. how likely users are to click on a given ad) because a higher CTR sometimes outweighs the benefits of a higher bid price." http://adsense.blogspot.com/2006/02/ad-rank-explained.html