Spam blogs are blogs that are RSS feeds full of useless content. This could range from simply re-directing other feeds or keyword stuffing the entries. The spam bloggers put advertising like AdSense on the websites and collect money from people who go to their site, find no valuable content so click on the ads to try to find what they were looking for.
These blogs make it very difficult to search with Technorati. The search results are full of useless entries. I sent them a suggestion to allow users to report spam blogs. This would allow them to remove spam blogs from their database. Of course this would require some human intervention, and I’m sure it would be costly.
Bloglines search seems to fare a little better. With Bloglines you can order the search by blog popularity (the number of subscribers). Spam blogs do not get subscribers, so they do not show up near the top of the search.
As long as blog search engines like Technorati link to these blogs, the spam blogs will be profitable to run. Search engines like Google go to great lengths to get rid of spammy sites from their indexes. Blog search engines need to start doing the same thing.