Are sites like Digg and Stumbleupon dofollow? I created a Digg about a Squidoo lens 27 days ago now and it's not showing up in any backlink check. Likewise, Stumbleupon is not showing up as a backlink to any of my sites - I added sites to Stumbleupon a couple of weeks ago.
Also, is there any advantage in SEO terms if you get lots of people to add your site to Stumbleupon or to Digg your site - say if 100 people all Digg or Stumbleupon your site then does this give Google 100 additional backlinks for Digg and 100 additional backlinks for Stumbleupon or does it just mean that your site appears higher up in the Digg and Stumbleupon index?
Would appreciate any thoughts.