How about adding OpenID (Google, Yahoo, AOL, etc.), Windows LiveID, Twitter, MySpaceID, and Hotmail support for registration and login and activity stream social publishing to allow your users to publish their comments here back to Yahoo, Twitter, Facebook, and MySpace.
This will make it much easier for anyone to participate and will also drive additional traffic back to your site from the social networks. Check out JanRain's RPX http://rpxnow.com for a free offering that provides all this functionality.
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