Digg recently added nofollow to some links on their site:
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.
I think this is pretty smart. Digg isn’t adding nofollow to everything, just the links that they’re less sure about. Once a story looks real to them, I can imagine that they would lift the nofollow. I discussed this for Google web properties in a recent video:
Google does something similar with Knol. Initially Knol authors received nofollow’ed links, but as we gain more trust in authors, we can remove those nofollows. As I recently said in another video, if a site like Wikipedia had good confidence in an editor, you could imagine links made by that editor not having the nofollow attribute. So if you have a way to determine which user-generated links are trustworthy, that could be a more nuanced measure of when to use the nofollow attribute. I discussed this subject a bit more in this video in case you’re interested. It’s about 1:24 into the video:
So new move by Digg is a positive change in my opinion, because Digg decreases the benefit for spammy stories but Digg still helps normal and high-quality stories in the search engines.