Social networking sites are among the most talked-about areas of content growth on the Internet. The term "social network" was coined in the mid-1950s by sociologist J. A. Barnes to describe interactions between people in the real world. When applied to the Web, it refers to Web sites where individuals with similar personal and/or professional interests can create an online "profile" and share information about those interests so others can read about them.

Friendster (http://www.friendster.com) was one of the first sites referred to by the "social network" label; however, later arrivals such as MySpace (http://www.myspace.com) and FaceBook (https://www.facebook.com) have become better known. Most of these sites give users the ability to post text, images, sound, and other information to their profiles. They often also include the ability to create a blog and/or chat with other users.

Classmates.com, which offers many of these functions, pre-dates those other sites, but was launched long before the "social network" label was applied to Web sites.

Recently, attorneys have been able to find information in social networking profiles that has made a difference in the outcomes of their cases. For example, Santa Barbara, California prosecutors said that information a woman posted about her partying lifestyle on MySpace.com was the difference between seeking a prison sentence rather than probation in a drunken driving crash that had killed her passenger.

Knowing how to mine this wealth of information that people post about themselves (or what their friends post about them) can be a boon to online researchers needing to find out background information on people, or to help locate someone who has gone missing.