Social networks are collections of people linked together on the web, often through a common interest or common set of acquaintances. Facebook and Twitter are two of the best-known social networking environments. The very large volume of message traffic over a social network enables data mining on a variety of issues, such as the intensity of viral infections in a geographical location. Social networks also enable collaborative problem solving at a previously unheard-of scale, as in the solution of a protein folding problem by over 50,000 individuals interacting over the web.
Image from socialmediahq on Flickr.