
Social Networking.
What is a social networking website? A social networking website is a place where others might find people that share similar interests to them, or are in some way connected be it through other connections related. Some of the most known Social Networking Websites are Facebook, MySpace and recently even Twitter.
How can a Social Networking Site improve search results. By promoting a website on a social networking site, people view this website as a reliable and trusted one. Promoting on one of these websites can not be done by spamming the network, but by posting updates on new features, or by letting the people that are following you, or in your network, that you have just posted a new article. It might take some time but it will make the website a trusted one. A trusted website is one that is visited more than once, meaning that people might even mention you in their own websites or articles, this can increase hits and inbound linking.
So does a Social Network affect a ranking? No, it doesn't. Not directly. But it does indirectly. If one optimizes their social network page it will help by providing exposure, the problem is you need to be found first, so Social Networking and SEO go hand in hand. They need each other to evolve into a high optimized search referenced website.
References:
http://www.conversationmarketing.com/2008/07/you-cant-separate-social-media-seo.htm
http://www.toprankblog.com/2009/06/is-your-web-site-seo-and-social-media-friendly/