Please note two things:
a) you can bid seperately for AdSense verus Serps. Beren and Nyet have explained how to do this. Content targeting not converting as well in the SERP? Just lower your bids..
b) smart pricing by Google is Google's attempt to address this problem. Basically, different adsense sites which don't convert as well will cost differently.
I think Google's real problem here isn't their poor implementation but rather their real lack of customer education
It appears that AWA has left it up to Beren and Nyet. I personally found this very frustrating, btw. However, I do recognize that this is probably just bad policy on the part of Google.
Regardless, in the end, you can bid seperately and if you don't want to for whatever reason, know that they are trying to do something about the different value of different clicks.
For more information, try "smart pricing site:webmasterworld.com"
I also suspect the smart pricing is Google's answer to lowering bids for Adsense.
The marketplace is a wonderful thing!
Smart pricing will likely work for the vast majority of users. Control freaks such as myself will however manually lower bids.
If it wasn't for getting 'branding' ads essentially for free, I would just leave it to smartpricing anyway.
Anyways, I spend *more* with Google now. Before, I just turned off content targetting.
For me, leaving it to Smart Pricing would double the cost of CPA and force me to turn it off.