As of 2012, there had been thousands of Google search algorithm updates. Some have been relatively minor while some like the recent Panda and Penguin updates managed to affect search results in significant ways and even brought penalties to some websites for overdoing their search optimization.
From the Google Dance or Boston update back in 2003 which focused on monthly index refresh, 2004 saw the rise of the Brandy update which changed the way SEO experts did their keyword analysis.
Google released the NoFollow update in 2005 that targeted spam on websites. As well as the Jagger update which focused on link farms, paid links, low quality links and reciprocal links.
In 2009, the Caffeine update was announced which resulted to major changes in crawling speed, expanded index and real time indexation and ranking.
It was announced in 2010 that Google utilized social signals from sites like Twitter and Face book for determining page rank.
The following year, 2011, Google released the most number of updates as of late including the various versions of the Panda Update which affected various sites.
2012 is not foreseen to be a year of even more algorithm updates. With the Google Penguin Update being recently released and with various sites being penalized, SEO experts are forced to come up with better ways to comply with Google’s standards when it comes to optimization.