I don't often get excited about new search technology. Ok I do get excited but not overjoyed. Ok in some cases I do.
My point is, I'm very happy to see Yahoo! entering the blog/communities space.
I've been talking internally how the engines need to move in this direction. Not just from a community support point of view, but also a search ranking relevancy point of view. No longer can a search engine aggregate data and serve results based on the "average" user.