This paper assesses some of the strong claims made about the significance of virtual communities to electronic commerce. It focuses on the notion of community building as a means to constructing virtual metropolises, where tens of thousands of individuals are engaged in public computer-mediated discourse. It is argued that the community approach discourages systemic analysis of collaborative media systems. In so doing, it distracts researchers' attention away from how the interplay of technology and content can both enable and constrain the growth of a collaborative system's user-population and participation. The paper proposes an alternative approach based on systems-theory. The model produced using this approach focuses on how to effectively expand contributions to, and use of a certain class of computer-mediated space, referred to as virtual publics. It suggests that an effective segmentation strategy is an essential element for those wishing to build a vibrant virtual metropolis. Segmentation strategy refers here to any systematic method used to split discourse spaces with the aim of creating a system of related virtual publics.