Attempts to impose knowledge management often ignore the vast organisational resource of workrelated tacit knowledge possessed by knowledge workers. Our research reveals that activities supported by social technologies such as Wikis, may provide a more appropriate capability for tacit knowledge management where a network centric focus is adopted. A corporate Wiki has the potential to engage the collective responsibilities of knowledge workers to transfer their collective experience and skills into a dynamic shared knowledge repository. However, the traditional organisational culture can be reluctant to allow this power shift which surrenders the monopolistic control of the few over the creation and management of organisational knowledge. In order to frame the theoretical perspectives of these new processes of creation, accumulation and maintenance of tacit knowledge in organisations, this paper uses Activity Theory to analyse the Wiki as a tool that mediates employee-based knowledge management activities leading to the democratisation of organisational knowledge.