Community membership has changed over the last decades. Most people participate in different communities simultaneously in order to satisfy different individual interests. This network individualism might threaten the sustainability of modern communities, like communities of practice (CoPs). In this paper we discuss the consequences of this notion for membership in a community. The unit of analysis in this paper is not a â€˜stand-aloneâ€™ community of practice but the multiple included individual as a node of various networks. This multiple inclusion is deemed to be important for the knowledge sharing between different CoPs. Taking this idea into account our analyses reveals the need to redefine the concept of â€˜legitimacyâ€™ in a community. Our underlying assumption is that broadening legitimacies facilitates multiple inclusion of an individual and, in this way, supports the sustainability of a community of practice.