There are 1000s of sites on the web that are built strictly for AdSense. Believe it or not I get traffic from these sites everyday.
IMHO these sites were not built to benefit a user. They are built to generate some income from AdSense. Even though I appreciate the traffic I get from them, I would prefer that these kind of sites would never be found in the SERPS.
Personally I think any site that is built (including directories) purely for AdSense should be excluded from the SERPS.