History
Before Google incorporated popularity into the SEO equation, search engines worked on relevance in terms of content. This was too easy to spam, because all I had to do was type the keyword on my web page one more time than you to rank first. Google introduced PageRank in the belief that if a site provided valuable content, people would link to it. This is a system that revolutionized the Internet as we know it.
As Google’s algorithm matured, so did the algorithms of other search engines, and the premise behind PageRank turned out to be incredibly effective. SEOs are always trying to better understand how search engines rank pages in order to better drive traffic to their own sites. Once linking as a ranking factor became popular, it became the focus of SEOs everywhere.
Links as currency
Search Engine Marketing’s job was to try to get links from a wide variety of sources to achieve the desired rankings. However, there is a problem. Pagerank flows through links. If you were to decide not to link to anyone, or place nofollows on your external links, your PageRank would accumulate, resulting in higher PR and better links for your pages.
Google understood that this was bad for their system. They were effectively incentivizing people to stop bonding. This did the same thing as getting people to stop spending money financially. It puts a key on the whole system! They began to prepare us for a change.
PageRank sculpting dies
Google started warning people in early 2009 not to rely too heavily on PageRank. Matt Cutts then reported on his blog on June 15, 2009 that Google reserves the right to honor or disrespect the nofollow tag on internal links. This was to invalidate artificial PR bundling methods on important pages of a website by placing nofollows on all links to unimportant pages. Google started to take control of its currency again.
The death of PageRank
By clustering your PR on important pages to rank higher, Google was effectively incentivizing people not to link at all. Google caught on to this and finally put the final nail in the PR coffin on October 15, 2009, by removing the Webmaster Tools metric. Questions arose, and Matt Cutts responded that PR was no longer factored into the rankings. That means that PageRank no longer existed as a ranking multiplier, but the links that made up PR were still taken into account.
Incentive to Link
For a while, SEOs lost their incentive to link to other valuable resources. To get the currency flowing again, they modified the algorithm to reward people for linking up. Suddenly the strategy has changed and linking is great for rankings. Linking is an economic policy that Google can heavily influence. Be sure to link to authoritative sites like Wikipedia on your own sites. Stay tuned for more SEO game changers in the future!