SEO Co-citation Analysis
There is a lot of talk in the SEO industry about Co-citation Analysis and how it applies to SEO. Most SEO's have taken what Rand Fishkin at SEOMoz has written and they have nearly all considered it a new trick to apply to SEO, even one that will "replace backlinks". This is false in both cases; it is neither new nor will it replace backlinks.
Google began as a co-citation engine. The original basis of Google's PageRank was to estimate a website's relevance based on the sites that link to it based on the study of author co-citation.
In academic papers people who quote a source also cite that source, or author. If two works cite the same author, work and especially same information, and those two works are in the subject then it assumes that the author being cited is relevant to that subject. When you have many papers citing the same author then it makes that author an authority on the subject. This is how it has worked with Google since the beginning.
Google founder Larry Page (the Page of PageRank) originally called it the "PageRank Citation Ranking". SEO's are just catching up to this little-known fact but are mistakenly calling it a new aspect of Google.
Although the manner in which Google views backlinks has changed the basis of why they're important has not. Backlinks today require much more work and quality backlinks are harder to obtain but once obtained they are longer lasting and far more beneficial. Spammy, irrelevant and for-sale backlinks are dangerous and can result in penalties.
If you want to learn about how co-citations apply to SEO or how the backlinking landscape has changed then feel free to contact us.