Andem - 12:02 pm on Aug 6, 2012 (gmt 0)
this is a kind of feature given to premium Adsense publishers because the url looks real - example.com/lr/popular-keyword/1288309/4/
These are not Google custom results. The pages simply have custom AdSense for Search ads.
They also somehow manage to automatically generate unique titles and meta descriptions
The meta descriptions are sometimes selected from a phrase which appears on the first search result page.
If you are going to report sites that are doing this, try to create a really off topic page. A current event might work well as you might be able to link to it and get it indexed quickly where it gets enough visibility to bring it to Google's attention. Link to that page from somewhere to get it indexed if you have to.
With perhaps tens-to-hundreds of thousands of unique visits from the SERPs per DAY, I'm sure Google has already taken notice of these results and done nothing about it.
I wanted to add: One of the sites I see the most also uses authorship markup for search results and gets an SERP listing with their profile headshot.