Yes, Digg will now officially "nofollow" your links. They recently made a blog post on it on the Digg Blog http://blog.digg.com/?p=864. I don't care about this, but I do know that a lot of people used this to help their websites in search engines. My advice is to focus on creating quality content. There are shortcuts, but they won't help your website in the long term. If you make quality content, other sites will link to you and that will really help! I checked the popular stories on Digg, and all of them are "do follow", but even big sites are "nofollow" in the upcoming section. I think Digg just makes popular stories Do Follow, and the rest are "nofollow".