An updated Google Groups thread has Googler, Jeremy Hylton saying:
We have launched a ranking change that reduces the number of results that are returned because of blogroll matches. There are still problems to work out, but this change appears to be a big improvement over our earlier fix. We had originally planned to launch an experiment for link: queries, but decide more recently to release this change first. We are still working on the link: change and expect to have that ready in a few more weeks.
We did expect to see an update for how Google Blog Search responds to the link query, but as Jeremy said, that won't be released yet for the next few weeks. But the blogroll matching detector, which matches for keywords in the blogroll sections of sites, should no longer return results for those keywords.
Why does this matter? Well, lets say you are like me and you track who links or mentions you via Google Blog Search. If someone has the Search Engine Roundtable in the blogroll, and the do a daily blog post, even if that blog post doesn't mention the Search Engine Roundtable, blog search would show that new blog post as a match. Why? Because it is in the blogroll and Google thinks it is part of the content of the blog post. Google said they fixed this issue but they do want feedback at the Google Groups thread.
Forum discussion at Google Groups.