Originally Posted by minstrel
...I'm unable to find any definitive information that would explain why only a few sites get those extra links...
Yeah, it's unclear, there are theories flying around though. Mr Google Patent (aka Bill Slawski, aka SEObytheSea) kicks a few ideas about here.
But for a definitive answer, I haven't found anything concrete. Product selling pages pop up a great deal, but is that through popularity of the page, or it's to do with click-throughs/pages-most-navigated-to?
Two things just occurred to me:
a) has anyone seen these extra links cropping up for sites where they haven't individualised their titles?
b) where are they getting their anchor text for these links from? Do a search for Adobe - they aren't getting the anchor text from the page titles, that's for sure. On the other hand, in some instances, like a search for cod
you can see the fourth link down is:
Academics | College of DuPage
That's a direct, exact title lift. So sometimes they use page titles, sometimes not. Well, that's cleared things up no end.
For link anchor text, the ones that aren't taken from the title bar, I can only assume come from most common anchor text in IBLs - stress 'assume' because just a few checks shows some flaws in that idea - specifically in which words are left out
of the anchor text link in the SERPs. Could be to do with the anchor text of internal links in the site. Possibly sitewide internal nav links.
It'd be nice to know why these links pop up, definitely. Site structure sounds like a good bet. Accessibility and compliance might play a part.
It's all guess-work though. But I don't believe for a minute it's about 'authority' sites - though I concede the 'nonsense' was a bit harsh - because that way we would all know exactly what the authority sites were, even if we didn't know why. Shortly after that, someone would quickly work out the criteria to fulfill to become an authority site.
There's always the possibility that Google is just trying stuff out - though this has been going on for 2 years now.