Rory Cellan-Jones traces the roots of social networking from the counterculture of the 1970s through early bulletin board systems such as California's The WELL and the first networks on the World Wide Web, finding out how a geeky hobby became a mass phenomenon. He discovers how Facebook became the world's biggest social network, looks at the sites of the future and asks where the phenomenon is heading.

His interviewees include Lee Felsenstein, co-founder of Community Memory, Larry Brilliant, co-founder of The WELL, Andrew Weinrich, founder of SixDegrees.com, Jonathan Abrams, co-founder of Friendster, Mark Zuckerberg, co-founder and CEO of Facebook, Chris DeWolfe, co-founder of MySpace, Michael and Xochi Birch, co-founders of Bebo, Wayne Ting, co-founder of Campus Network, David Kirkpatrick, author of The Facebook Effect, Biz Stone, co-founder of Twitter, Dennis Crowley, co-founder of Foursquare and Reid Hoffman, co-founder of LinkedIn.