Although Virtual Communities (ViCs) have been considered as an important e-commerce instrument, little is known about their evolution and the changes in the communication activity of its users. A frequent finding is that a small number of the participants is responsible for the majority of messages and, in contrast, a large portion of the users only write one or a few message(s). This discrepancy deserves more attention. In this paper, the heterogeneity of the communication activity is examined longitudinally on the basis of the graph-theoretical models "Random Network Theory" and "Scale-free Networks". The fusion of these two models allows operationalization of the heterogeneity of the relational as well as the attributive communication activity in ViCs. The adjustment of the empirical distribution functions of the examined ViCs to this model shows a predominance of preferential over uniform binding. This "rich get richer phenomenon" proves temporally stable and leads to the emergence of heterogeneity of the member's activities. We conclude that instead of stimulating all participants, it appears to be more promising to address the lead users as a main target. Their attachments to other users may be utilized in a positive and amplifying way in order increase a community's communication activity
