Use of social network in SEO

[stephen55]

Social Networking allows visitors to share quality links through public websites. This means that when a visitor likes your site, he / she can easily recommend it in his / her favorite social networking portal.
Basically, social networks are similar to search engines - the goal is to bring the most interesting and relevant content to the top of the site. In sites like Facebook and MySpace for example, you can measure your popularity by the number of friends or visitors you have. On Twitter, getting more followers is most important.

[AthenBoyle]

Yes I agree with you, However, I don't think that social networks are helpful to SEO or there is DIRECT connection between Social network and SEO.
But both Social network and SEO are walking towards same goal which is getting traffic to website and maintain reputation