A social network service focuses on building online communities of people who share interests and activities, or who are interested in exploring the interests and activities of others. Most social network services are web based and provide a variety of ways for users to interact, such as e-mail and instant messaging services.

Social networking has created powerful new ways to communicate and share information. Social networking websites are being used regularly by millions of people, and it now seems that social networking will be an enduring part of everyday life. The main types of social networking services are those which contain directories of some categories (such as former classmates), means to connect with friends (usually with self-description pages), and recommender systems linked to trust. Popular methods now combine many of these, with MySpace and Facebook being the most widely used in North America;"Social Nets Engage in Global Struggle" - 66% of MySpace and Facebook users come from North America: Adweek website. Retrieved on January 15 2008. Nexopia (mostly in Canada); Bebo, Facebook, Hi5, MySpace, Tagged and Skyrock in parts of Europe; Orkut and Hi5 in South America and Central America; and Friendster, Orkut, and Cyworld in Asia and the Pacific Islands.

There have been some attempts to standardize these services to avoid the need to duplicate entries of friends and interests (see the FOAF standard and the Open Source Initiative), but this has led to some concerns about privacy.

History of social networking services

The notion that individual computers linked electronically could form the basis of computer mediated social interaction and networking was suggested early on . There were many early efforts to support social networks via computer-mediated communication, including Usenet, ARPANET, LISTSERV, bulletin board services (BBS), and EIES: Murray Turoff's server-based Electronic Information Exchange Service (Turoff and Hiltz, 1978, 1993). The Information Routing Group developed a schema about how the proto-Internet might support this.

Early social networking websites included Classmates.com (1995), focusing on ties with former school mates, and SixDegrees.com (1997), focusing on indirect ties. User profiles could be created, messages sent to users held on a “friends list” and other members could be sought out who had similar interests to yours in their profiles. Whilst these features had existed in some form before SixDegrees.com came about, this would be the first time these functions were available in one package. Despite these new developments (that would later catch on and become immensely popular), the website simply wasn't profitable and eventually shut down. It was even described by the website's owner as "simply ahead of its time." Two different models of social networking that came about in 1999 were trust-based, developed by Epinions.com, and friendship-based, such as those developed by Jonathan Bishop and used on some regional UK sites between 1999 and 2001. Innovations included not only showing who is "friends" with whom, but giving users more control over content and connectivity. Between 2002 and 2004, three social networking sites emerged as the most popular form of these sites in the world, causing such sites to become part of mainstream users globally. First there was Friendster (which Google tried to acquire in 2003), then, MySpace, and finally, Bebo. By 2005, MySpace, emergent as the biggest of them all, was reportedly getting more page views than Google. 2004 saw the emergence of Facebook, a competitor, also rapidly growing in size. In 2006, Facebook opened up to the non US college community, and together with allowing externally-developed add-on applications, and some applications enabled the graphing of a user's own social network - thus linking social networks and social networking, became the largest and fastest growing site in the world, not limited by particular geographical followings.