This document discusses social networking as a Web 2.0 tool. It provides background on early social networking sites like SixDegrees.com and highlights popular current sites like Facebook, Twitter, and LinkedIn that have hundreds of millions of users. The document outlines the structure of social networking sites including profiles, friends, groups, discussions and blogs. Both advantages like easy communication and reaching wide audiences, and disadvantages like viruses, spam and lack of control are covered. Social networking is summarized as a participatory web platform that harnesses collective intelligence where users create value by connecting with others.