Since many blog authors don’t publish full feeds for a variety of reasons, the Google Blog Search has been missing a lot of what is posted in blogs. If a blog author posted a partial feed, Google didn't index links or the full text of the post which means the links and full text was not found in Google Blog Search.
Now Google says:
With Google Blog Search you don't have to search each blog individually, but can search all blogs (and only blogs) at one time.
We have changed the way we index blog posts to include the full content of the page. We've had occasional complaints about the use of the feed content, particularly the problem with partial feeds. The indexing change has improved the results for a lot of queries, both because we have the full content of the page and because we extract links that are missing from the feeds.
Today, many of the top genealogy sites announce their new databases on their blogs - with surnames. Other blogs are devoted to research on particular ancestors - so a search of genealogy blogs could help you find repositories of otherwise unknown family tree information.
Some ideas to search for are ancestor surnames, genealogy topics, vital records, ancestral locations, or living relatives.
Blog Search is Google search technology focused on blogs. Google is a strong believer in the self-publishing phenomenon represented by blogging, and we hope Blog Search will help our users to explore the blogging universe more effectively... Blog Search enables you to find out what people are saying on any subject of your choice.
You can choose to search posts from the last hour, last 12 hours, last day, past week, etc. so that you don't duplicate your searching effort. If you have previously used Google Blog Search thinking you have searched complete posts, you may want to do some re-searching.
You can also subscribe to 'blog alerts" to automate your blog queries for surnames and ancestral towns. You will receive an e-mail when your query keywords are found in a blog.
To create a query so that only genealogy blogs are searched, be sure to add ~genealogy to the query along with your surname or other keyword.
Easy Genealogy Google Searcher, Part II
The blog search is also part of the Easy Genealogy Google Searcher, Part II