Google’s Matt Cutts explains in the video below how links from social media websites such as Facebook and Twitter are treated. In summary, they’re treated exactly the same as links from any other website, in that each additional link contributes to the perceived importance of the destination page proportionately to its own importance. There’s an important caveat though: Twitter links are nofollow, so Google (nor Yahoo or Bing, who also respect this rule) won’t be attributing PageRank to your website on the other side of the TinyURL. Facebook links are not nofollow, but since most user’s pages are private, they can’t be crawled, so again you won’t gain any direct ranking advantage here.
So what does this mean? Should you spend less time considering how to embrace social media? Of course not. Social media websites can be used by website owners in many ways: as a channel to reach (sometimes niche) audiences; an extension of customer services; to form communities and engage users in discussion; to help understand future market trends & requirements. It’s good to know where we stand and earning additional importance from public profile pages linking to your website is a pleasant bit of icing on the social media cake, but this should never have been anyone’s main reason for incorporating social media into their marketing plan.