Dave Gullo stashed this in Google!
Being a bootstrapper of a business (stupidly and soley) dependent on organic search results primarily from Google, I can tell you first-hand that The Google gaveth, and MOST certainly tooken away with.
In late 2008 they turned the knobs to favor traffic over lexical richness and heuristics and their earnings and value has regained the slump and stayed relatively strong. This decimated a vast portfolio of SERPs that ultimately destroyed our business.
Now, the government is looking into search manipulation of results. Google geting more trouble from FTC:
In creating such a huge marketplace, Google gave huge incentive to game their system.
With so many people trying to game the system, what choice did Google have other than to hurt large swathes of SEO?