One of my many search and social conspiracy theories (of which often turn out to be true) is that the Penguin algorithm update on April 24, 2012, was actually two updates. There was a public update that went after low-quality links, splogs, and other SEO linking tactics. This sent shockwaves through the search engine optimization world. Most agencies had to change some of their practices. Some closed down altogether. It was the SEOpocalypse for many in the industry.