Future of Web Apps - London 2007
Kevin Rose gave an interesting talk at FOWA about communities and how the Digg team is constantly having to keep their site algorithms updated to avoid gaming and spamming attempts by users. 
He discussed the fact that as the site has grown in number of users, which now tops 900,000+, that the robust discussion is lacking and a few users tend to break out in fights back and forth in the comment sections.
He said they are looking at way to reduce the size of the groups by customizing digg even more so that people that have common interests like Audi, and tea, would see the same stories.
This would be done by leveraging the “attention data”, which is basically the stories you digg and how often on the site to group users more closely together.
Kevin also discussed today that digg will support the use of OpenId in the near future. See the tech crunch DIGG Adopts OpenID about it.