The Internet creates a very unique environment where numerous individuals and widely distributed organizations can communicate and even collaborate for common interests. Virtual communities, shared information databases, and online forums are visible examples of the self-organizing social collectivities, which emerge from the many-to-many interactions among voluntary participants. Online social communities exemplified by blogs and social networking sites are getting more and more attention nowadays from the business sector, and companies are eager to find ways to use them for business opportunities. Despite the mushrooming hype regarding the unlimited potentials of virtual community, little is known about its complex nature-how virtual communities are born, sustained, and under what circumstances they collapse. A virtual community is an aggregate of voluntary participants, in which individual behaviors are in conjunction with the behaviors of others. People decide to contribute or free-ride in response to the contributing or free-riding behaviors of others. If many people already are contributing to the community, for example, one may be strongly tempted to free-ride, while this may not be the case if there are very few contributors. Understanding this social interdependence is the key to grasping the collective dynamics underlying virtual communities. This book aims at illuminating the implications of the collective social dynamics in a computer-mediated environment on advertising, business, and communication in general. Along with conceptual discussions, this book shows some experimental findings related to the psychological and social-structural factors affecting individuals' communicative motivations. "This pioneering book should be valuable to read since it is one of the first academic attempts to shed light on how network structures influence the behaviors of individuals on the Internet." - John D. Leckenby, Professor and Everett D. Collier Centennial Chair in Communication, The University of Texas at Austin