The notion of community has been at the heart of the Internet since its inception. For many years, scientists have used the Internet to share data, collaborate on research, and exchange messages. In essence, scientists formed interactive research communities that existed not on a physical campus but on the Internet. Within the last few years, millions of computer users worldwide have begun to explore the Internet and commercial on-line services such as Prodigy and America Online. Many have joined one or more of the communities that have sprung up to serve consumer needs for communication, information, and entertainment. One of the oldest virtual communities is the Well, launched in 1985 by a group of high-tech enthusiasts located primarily near San Francisco. (See the sidebar “Visit an Electronic Community.”) Over the past decade, thousands of computer users have communicated with one another through the Well and, over time, developed strong personal relationships off-line.