A social networking service is an online service, platform, or website that focuses on building and reflecting social relations among people.
A social network service essentially consists of a representation of each user (often a profile), his/her social links, and a variety of additional services. Most social network services are web based and provide means for users to interact over the Internet, such as e-mail and instant messaging.
The main types of social networking services are those which contain category places (such as former school-year or classmates), means to connect with friends (usually with self-description pages) and a recommendation system linked to trust. Popular methods now combine many of these, with Facebook and Twitter widely used worldwide. MySpace and LinkedIn being the most widely used in North America. Nexopia (mostly in Canada), Bebo, Hi5, Hyves (mostly in The Netherlands), StudiVZ (mostly in Germany), iWiW (mostly in Hungary), Tuenti (mostly in Spain), Nasza-Klasa (mostly in Poland), Decayenne, Tagged, XING, Badoo and Skyrock in parts of Europe. Orkut and Hi5 in South America, India and Central America, and Friendster, Mixi, Multiply, Orkut, Wretch, renren and Cyworld in Asia and the Pacific Islands and Twitter, Orkut and Facebook in India.
Why do I say that social networking suck?
Because in essence it has very little to do with actual social interaction and because in many cases it prevents people from real social value!
— source unixsheikh.com | 2010-11-18