Digg adds nofollow to some links
Theyâ€™ve made a few changes to the way Digg links to external sites that may impact some folks in the SEO community. These changes reduce the incentive to post spammy content (or link spam) to Digg, while still flowing â€™search engine juiceâ€™ freely to quality content. Theyâ€™ve added rel=â€ťnofollowâ€ť to any external link that were not sure and can vouch for. This includes all external links from comments, user profiles and story pages below a certain threshold of popularity.
This work was done in consultation with leading experts from the SEO/SEM and link spam fields, in an effort to lookout for the interests of content providers and the Digg community. As always, Digg will closely monitor these changes in the wild and iterate based on feedback.