1script - 6:02 pm on Aug 6, 2012 (gmt 0)
@netmeg and @indyank: Guys, we are definitely talking about premium AdSense publishers, *not* CSA. I've never seen CSA results in Google SERPs and I also believe it's an easy fix for them if any of those pages ever creeped in. Premium publishers are able to change many things in the ads and especially two of the most important: the exact size of the block and the fonts of the titles. Everyone has their eyes trained on 300x250 blocks with Verdana titles and it takes people 0.1 seconds to realize that this is an ad and, if they feel really annoyed, report that to Google. Premium publishers are able to blend in much easier and I have no doubt they get reported less.
Anyhow, getting back to the issues of search pages in Google's SERPs: indyank is right, they don't always have the word "search" in their URL or content - perhaps this is what lets them fly under the radar? They are still dynamically generated doorway pages that contain no information about the product/issue, only something that is "related", usually a list of links to other pages, and sometimes it is only so vaguely related that you're amazed it's ranking for the product name with just a title and H1. BTW, indyank, I should check if it's really H1 - you're right, it may just be styled as the largest header but not marked as H1.
I did, however, come across some of those ranking search pages that do indeed say "search for #*$!" on them. There can also be "tag" pages ranking etc. So I would call all these "doorway pages" which is what they are - they are only leading to other pages of the site. And that's in best case scenario because sometimes there's nothing to lead to, yet they still rank.
Bottom line: Google lets large sites get away with doorway pages - something that was a no-no since the dawn of Google.