Robert_Charlton - 9:59 pm on Aug 1, 2010 (gmt 0)
As I'm seeing it right now... the "Pages similar to..." links appear in the footer when you search for company or organization name... or, in the case of very large companies, by company division. They don't appear when you do a keyword search for a product or service.
A search for [wikipedia], eg, returns links in the serps footer for...
These are the top 4 results taken from the serps page you'll see if you click the "Similar" link next to the "Cached" link for Wikipedia (but only if you've searched for "wikipedia").
I see the "Similar" link appearing on most searches, but not always on every result... and they appear to be query related rather than simply site-related.
Looks like you can get a sense of how (and if) a site is branded and get a glimpse of who the site's peers are by searching for the company name.
The results are not the same as seeing who ranks for a keyword search for a general branding category. Eg, though Radio Shack is one of those sites (discussed a while back when we talked about branding) that ranks for "electronics"... presumably because of branding... the sites returned for the "electronics" search are not necessarily the same as those returned by the "Similar" and "Pages similar" links on the [radio shack] search.
It's interesting that Amazon is so broad that it doesn't return "Similar" links. You have to narrow your search to [amazon books], eg, to get the "Similar" links... and I've seen this particular example come and go.