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Regarding SEO, there are direct and indirect benefits. Among them: Constantly fresh content and changes to the site (signaling to the SE's that somebody is home at the site and that there are reasons to keep coming back often), and the fact that the more useful and relavant you can make your site to it's contingent, the more likely site visitor/users are to bookmark the site and link to it.
All part of the grander scheme: Make the site as appealing and useful to its user base as possible.