"In May, 2010, Matt Cutts denied that social signals had an effect on search rankings. In December of the same year, he declared that they were actually starting to work in the buzz and signals they were able to get through social media into the site authority factor of their ranking algorithm. Six months later, Google+ was born.
The Penguin Update and subsequent tweaks to it have changed the way that search engine marketers approach aggressive optimization. The days of running rampant and blasting out bulk links are gone. Today, quality finally trumps quantity and the playing field has been leveled in a way that in essence puts a "governor" on how quickly they can ramp up the rankings on their domains.
As social signals grow in their effects on search rankings for both Google and Bing, the ability to create amazing content and promote it on social media is quickly becoming the most important technique that internet marketers have in their arsenal. In 2013, it will likely eclipse link-building as a ranking factor.
Here are three things you must understand to make it work for you today and to be ready for what lies ahead".
Via Antonino Militello