Here is the video posted by Barry Schwartz. He tells about the difference between the unnatural links and Penguin update. He also cover some other topics like.
1. Google Ignores Links From Updowner.com
2. Google Panda 3.8
3. Disavow links tool launches by Bing for win Seo hearts
4. Google release video for help Seo's
5. Why Google video stop at 301 views
6. Affiliate links should be no follow