http://blog.digg.com/?p=864
We?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 ?search engine juice? freely to quality content. We?ve added rel=?nofollow? to any external link that we?re not sure we can vouch for. This includes all external links from comments, user profiles and story pages below a certain threshold of popularity.
My comment:
Big impact on those using digg to get indexed quickly. As for SEO value, getting the link's no follow tag removed depends on the popularity of your content. Popularity = 'real content' Unpopular content = spam. I'm not sure the distinction is that black and white.
