tedster - 7:53 pm on Aug 30, 2010 (gmt 0)
This is not the regular Blog Search - it's a new filter that appears on the regular organic SERP that helps you identify entire blogs focused on your query term.
Recently, our blog search team made it much easier to find full blogs about your query, rather than single posts on the topic. This is especially useful if you're looking for bloggers that post on an ongoing basis about the subject of your query. Try it with one of your search queries by clicking "Blogs," then "Homepages," in the left-hand panel of your search results.