I haven't really commented on the "should blogs be in Google search results" debate, but one random question. What is a blog? What's the technical difference (from the perspective of a search engine) between my blog and The Register? I don't see how you can "filter" blogs. You can obviously change the page ranking mechanism to give certain types of sites an advantage or disadvantage, but I don't see how you can filter blogs. My blog is just a bunch of html created by a content management system.
If more people think that the google search results are poor because the top results are not "relevant" it means the ranking system is broken, not that something has to be "filtered". The whole point of a search engine is that it searches everything and finds the most relevant pages.