A few weeks ago Danny Sullivan wrote a very interesting article on Searchengineland in which he discussed the use of social signals in the rankings of both Google and Bing. He had approached representatives of both search engines who both said they were using Twitter and Facebook links as a ranking signal.
In his webmaster help videos Matt Cutts last week confirmed this. And not only that, he added some more information to it. He said that they are also “trying to figure out a little bit about the reputation of an author” on Twitter or Facebook, something he said they didn’t do in May this year. They changed that since May. See the video here:
They are studying how they can use these signals even wider. In the video he also takes a sneaky stab at Facebook. He explicitly explains that when Google cannot crawl a page they cannot assign Pagerank. “If for some reason a page is forbidden for us to crawl or we are not able to obtain it somehow than we wouldn’t be able to use that within our rankings”. Facebook data therefore is probably less important than the Twitter data.
They are using it relatively lightly Cutts said. And he cautions people not to go crazy on getting number of followers. The quality of followers therefore also count.