matrix_jan - 9:00 am on Feb 26, 2013 (gmt 0)
source from within Google
Don't know about sources from withing google, but WT lists tons of links from pinterest. Why would they list it if they have no value?
There are tons of websites with 0 or 1 pagerank that outrank PR5+ websites. Average users don't have access to creating follow links, they share, pin, tweet. And user behavior is a major ranking factor.