Idea: blog indexing

Blog index/blog directory with ongoing (rather than annual, say) blog ratings submitted by users who are also able to add comments (see here for inspiration on this aspect). Why this idea? Because blogs aren’t picked up by search engines and Technorati appears to require bloggers to add tags manually (which seems to invite the same sort of problems that getting people to add metadata to their content in CMSs). I’ve yet to encounter such a directory and most of the blogs I’ve found useful have come on the back of del.icio.us, webpage recommendations or similar. I feel like I might be missing out on a lot. Not sure what the possible revenue opportunities would be apart from discrete banner ads, but it might open up potential opportunities.