In order to seek more effective ways to design and support online communities of practice, we examined how Wikipedia, a large-scale online community of practice, is developed and emerges over time. We conducted a Delphi study to explore the social, organizational, and technical factors that Wikipedia experts believe have supported the evolution of this community. Based on the findings, we present a model for thinking about online communities of practice and suggest it may serve as starting point to develop strategies of designing and supporting online communities of practice.