Decline of Organic Links - another great infographic from Aaron Wall at SEOBook - but, oh so discouraging whether you are a searcher or responsible for a website.
There is a lot in this that is very damming of Google's practices. Yes - it has to fight the people who game the system; but no - it shouldn't be favouring its adwords and properties, and very likely the Google engineers have gone too far in penalizing websites for some practices.
Of interest - we think that putting links in postings on Facebook or tweets will help build authority - but most social media sites put the no follow tag around outbound links thereby turning off authority.
Conclusion: "For many years it was true that SEO = links, but due to the rise of rel=nofollow, fearmongering & social media, organic links have lost much of their relative importance in many verticals."