Bill Slawski started a Cre8asite Forums thread on the topic of a new patent application he spotted named Ranking blog documents. Bill expained this document in great detail at his blog post named Positive and Negative Quality Ranking Factors from Google’s Blog Search (Patent Application).
He summarized the document for the forums, which makes it perfect to quote here.
What positive factors contribute to a blog ranking well in Google Blog Search?
How many RSS subscriptions there are to the blog, How often people click on a link to the post in search results, How many blogrolls the blog is in, How many "high quality" blogrolls the blog is in, If the blog offers visitors the chance to tag posts, whether people are tagging them, References to the blog by sources other than blogs, Pagerank, and; Others.
What negatives factors contribute to a blog not ranking well in Google Blog Search?
If new posts appear in short bursts or at predictable intervals, If the content of the posts doesn't match the content of feeds from the posts, If the content includes a lot of spam related keywords, If a lot of content is duplicated in multiple posts from a blog, Whether posts are the same size, or roughly the same size, Link distribution of the blog, If posts primarily link to one page or site, and; Others.
Personally, I am more into the negative factors in helping blog search relevancy than I am with the positive factors.
Forum discussion at Cre8asite Forums.