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If you`re interested in SEO, then you should subscribe to www.sitepronews.com newsletter. They always have good articles (dunno if they are original or “private label articles”).
Latest article by Eric Lester is about exploiting in google`s algorithm and how one guy filled Googles index with few billion sp@m pages. He explains that Google indexes each subdomain as independent, so on one domain you could generate countless pages with keywords and AdSense ads. In some previous article they stated, that subdomains add PR to the original domain, so this is even more useful for those who practice “artificial SEO”.