Toward a “Critical Mass” Theory of Interactive Media

This article proposes a “critical mass” explanation for the diffusion of interactive media, such as telephone, paper mail systems, electronic mail, voice messaging, or computer conferencing, within communities. Interactive media have two characteristics not shared by many other innovations. First, widespread usage creates universal access, a public good that individuals cannot be prevented from enjoying even if they have not contributed to it. Second, use of interactive media entails reciprocal interdependence, in which earlier users are influenced by later users as well as vice versa. Consequently, interactive media are extremely vulnerable to start-up problems and discontinuance. Traditional explanations of diffusion of innovations do not accommodate these two properties of interactive media. The influence of these two properties on the probability and extent of interactive media diffusion within communities is the focus of the critical mass theory developed in this article.