I ran across this thread:
In it Drall makes a statement about how their approach to Adsense placement is one that minimizes accidental clicks. Their idea is that intentional clicks provide a better ROI investment for the advertiser. Because Drall's sites provide good advertiser ROI they aren't smartpriced so much and therefore even with a lower CTR they earn more than they did when they had an Adsense placement that was more likely to produce accidental clicks.
Drall also talks about how it was difficult to make this change (no guarantee of a positive outcome). They saw an initial drop in earnings until what they perceived as smartpricing changes started to take effect (two months later).
I personally would do anything with my sites that would add to their long-term value. Short-term money is never the goal. I would definitely consider re-evaluating the Adsense placement on my site, if the Adsense program wasn't such a black box.
If I make a change that in the short-term creates an income draw down, that's fine. I can measure that. What I can't measure (isn't shared by Adsense) is some sort of quality indicator that helps me know if my changes are improving the ROI for the advertiser. I also have no way of knowing how long I will have to endure the draw down until possibly the smartpricing algo recognizes the improvements and rewards me (in terms of smartpricing, is my site evaluated daily/monthly/quarterly before some sort of change is implemented?)
I don't make changes with my site because "if its not broke don't fix it." I'm making money, why not go with the sure thing when there is absolutely no concrete evidence that making changes will improve things. (Even Drall's statement is simply anecdotal. With the way Adsense is right now, there can't be any A-B type testing in a matter such as this.)
Of course Adsense is doing the exact same thing, just making cash and not fixing something that's not entirely broken. If they were serious about improvements in the program they would stop making up nebulous rules about ad placement (blend your ads, oh wait now we don't want you to blend in your ads. Ads can be on the same page as pictures of products, but not too near. Don't draw attention to your ads- how do you mean, by not putting them in the middle of the page's content-oh wait, that is allowed) and give us some tools to quantify matters with.