Both Google and Bing stated, in an interview with Danny Sullivan, that they do use data from Twitter and Facebook to organize search results. It may be that this is the beginning of the growth and that SEOs around the world will have to hold their colorful hats and enjoy the ride, this might change SEO completely.
When Google’s representative responds to Sullivan’s question about the use of Tweets as a signal for a page’s authority, the answer is crystal clear:
Yes, we do use it as a signal. It is used as a signal in our organic and news rankings.
People in the industry have speculated a lot about Google and Tweets in the algorithm, especially since they bought into the data stream of Twitter. It is now confirmed that this is the case, the question is how much impact it has. Google, as we all already know, have a long list of factors that influence their search results and if an RT (retweet) means very little in comparison with for example Meta Description, maybe it’s not something worth spending weeks getting. My small tests indicate that this is precisely the case, long term effects are small even if it may seem that in the short term, it is important.
The most exciting about this is that it might mean that Google will make more use of the social profiles, which sounds likely. If Google were to choose to prioritize the Tweets and Faebook likes, it would change the search engine optimization substantially and probably create an even greater demands on the combined PR / Social Marketing / SEO.

