I've been wanting to post about this for a while, but I figured it would resolve itself after a couple of months but that hasn't happened yet.
This is different from tag pages, continue reading. There are several high-quality sites which have taken advantage of their status as an authority in order to link to search result pages from other parts of their site. These pages eventually rank and thanks to Google's abandonment of the "one or two pages from the same site" on the SERPS, I'm running into page 1, 2, 3, 4 and above which contain 90%+ of internal search result pages from authority sites.
I really got annoyed today when I was looking for something that only we offer (a 100% free, non-ad-supported service and trademark) and it appears that one site has created search result pages from keyword lists and now ranks 1st page, often above the real site for countless terms.
The general layout of virtually all of these pages are search results, 2-3 AdSense for Search custom ads as the first two "results" and then mildly rated pages to completely unrelated pages (many are registered trademarks). URLS look like:
site.com/s/this-and-that-for-the-other
The problem is that these sites are using their authority status to rank for stuff that they don't have, nor do they offer. The stuff they rank for really looks like they are generated from database compiled from Alexa or AdWords data. One site has over 50 million search result pages listed while others have between 10-40 million. Ridiculous.
This has been going on for months and it isn't fair to anybody. I've used the G Search feedback form several times hoping to raise some flags because it is frustrating as both a user and an original content producer.