The Sociology of Web 2.0
It's important to realize that these ventures are not all examples of the same thing. There are differences that run deep, both in the nuts and bolts of the businesses/sites/services—technology, function, and the like—and in the social structure of the community they are built around.
The social aspects of these communities, such as how they are constituted, the degree to which values are shared among members, the sharing of interests, the demographics of group membership and openness of membership, all have implications for the type of technology that will work and the uses to which the site/service can be put. It may actually be useful or necessary to know something about sociology or social psychology, or at least have good intuitions about these fields, to build successful Web 2.0 sites and services.
Maybe one can get by with freshman sociology concepts like "Gemeinschaft" and "Gesellschaft." According to Wikipedia (hey, we all do it), German sociologist Ferdinand Tonnies intended these terms to describe ideal types of social structures, and assumed that actual social structures would only approximate their characteristics. But the distinction the terms draw seems useful for sorting out different kinds of Web 2.0 businesses on the basis of their social structures.
"Gemeinschaft (often translated as community) is an association in which individuals are oriented to the large association as much if not more than to their own self-interest. Furthermore, individuals in Gemeinschaft are regulated by common mores, or beliefs about the appropriate behavior and responsibility of members of the association, to each other, and to the association at large..."
Gesellschaft (often translated as society or civil society or "association"), in contrast, describes associations in which, for the individual, the larger association never takes on more importance than individual self interest, and lacks the same level of shared mores. Gesellschaft is maintained through individuals acting in their own self interest. A modern business is a good example..."
Trust operates differently in these two models. In the Gemeinschaft model, trust may flow naturally from the common values of the members, while in the Gesellschaft model, it may be necessary to build-in mechanisms to justify trust.
