Speculation is rife that Google may be using the Akismet spam filter data to penalize website rankings.
Google has been issuing a lot of warning to webmasters about unnatural linking practices. Webmasters have been getting warning messages about using techniques that are outside of Google webmaster guidelines. The warnings mention that the websites could be using unnatural linking practices intended to manipulate page ranking. They also urged the webmaster to change the website so that Google quality guidelines are met and then submit the site for reconsideration to be included in the search results.
Till now, nobody knew how Google zeroed in on which websites to penalize, especially since they did not mention anything specific about the URLs that are causing the problem. One of the webmasters noticed that the example URLs that Google had shared was never even published on any website because they were caught by the Akismet filter.
This is what leads experts to speculate that Akismet data is what Google possibly uses to decide on unnatural linking practices.