Networks and the World Wide Web seem to provide an answer to efficiently creating and disseminating knowledge resources. Knowledge, however, is ambiguous in character, and contains both explicit (information) and tacit dimensions - the latter being difficult to value as well as to transfer. Participant identity, commitment and behaviour within the network also affect the sharing of knowledge. Hence, existing laws and norms (including property rights) which have been established on the basis of discrete transactions and monetary value-oriented exchange may (...) not be adequate to deal with the whole spectrum of knowledge transfer. A model is needed to address transfer across a large heterogeneous network. We introduce the concept of sub-networks where tacit knowledge resides and argue that considering social norms underlying trust and other informal mechanisms provides a more suitable basis for understanding the exchange of tacit knowledge. Norm establishment is complicated by the fact that values differ across cultures; however, the social norms that underpin sub-networks can sustain knowledge transfer within them. The purpose of this conceptual article is to introduce the concept of sub-networks and to identify the sub-network/network relationship as an area in which it is necessary to look beyond property rights and raise the issue of norms. We believe that an analysis of the role of social norms in knowledge sub-networks and their interaction with global networks points to a key element in understanding networks and any emerging theory of network ethics in the twenty-first century. (shrink)