Bones - 9:28 am on Mar 5, 2008 (gmt 0)

But there are many major corporations and ecommerce sites with page counts in the millions that don't show up.

It does seem a bit random. I imagine that qualification is (at least partly) based on some actual site traffic data, either gathered from Analytics, the toolbar and/or search queries.

As a user I like it, but I'm not convinced that showing this for queries such as "Altavista" is appropriate. "Search altavista.com" doesn't really produce the results that I think most users would expect when they hit the button.