This paper revisits Irving Janis’ theory of groupthink in the light of the ongoing debate on legitimate peripheral participation in communities of practice. We argue for a movement in perception from the linear development of community formation to a multi-dimensional model based upon the inter-relationship of the domains of community, practice, meaning, and identity. Janis’ theory of groupthink is outlined and communities of practice defined. From these definitions, we go on to examine the significance of in-groups and out-groups, applying Janis’ model to patterns of collaboration and situated learning.