SEOmoz’ Search Engine Ranking Factors is probably in the top 10 of the most valuable pieces of SEO documentation online. Where else can you find over one hundred years of SEO experience on one page? While link value is one of the factors being discussed in this piece of research, I would have loved to see more about this subject. And this is why I tried to do the same for link value influencing factors.
17 Link building and SEO professionals have shared their thoughts about nearly 40 different factors that might (or might not) influence the value that search engines can assign to a link. These opinions have been bundled into one document: The Link Value Factors.
Like stated in both the intro and the comments, it’s nearly impossible to design a piece of research that is 100% accurate. Especially when it comes to links, because no two links are exactly the same and no two links will be treated exactly the same by a search engine. In my opinion, however, the page with Link Value Factors is an in depth piece of content that can serve as link building background info for both link building newbies and pros from the field pretty darn well. Enjoy!