No follow makes sense when you look at the big picture, but many webmasters want to continue the run and gun link selling scams of the past.

Google gives you a choice, use no follow on user generated content or when you sell links or lose your credibility with Google and your traffic when we devalue your pages.

I agree that any website that blatantly sells links (Page Rank) should be shot down, this includes those who are scamming along with contextual link networks, spamming blogs, spamming forums which is all search engine spamming in the end.

Google is correct for fighting this and devaluing websites that engage in this sort of conduct, I would do the same thing to any site that is allowing posting agent script operations to spam their pages (De-index the URL's in bad cases the entire domain).

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