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They have typically 4 links below the serp, these are internal pages also related to the search terms. I believe this is a new thing for Google, in addition like they think the site is a real Athority on the keyword/keywords searched for.
I did check out some company names, and sure enough some of the big companies have same thing, a couple, Newegg(great computer parts) and General Electric, had the same deal.
Well mine had it, and it sticks out like a sore thumb amongst the other serps, looks "like special treatment".
And here I thought I might have been special ;(
On the "Real Estate" search mentioned above, not all the sub-links go to the domain of the #1 listing. Strange.
No but the sub-link is a link that exists in the page of the main link, in fact in a very prominant position.
I'd say G is looking at what people click on most when they get there, info they could only have from their toolbar