The Web 2.0 model has aroused vast attention as it alters the traditional role of Internet users as pure information receivers. Wikipedia, as one of the most successful case of the Web 2.0 model, creates an online encyclopedia through the collective efforts of volunteers. Shared freely by all Internet users, it forms an online community platform on which users can seek and share knowledge. This study investigates the factors that affect the adoption of Wikipedia. Based on the TAM of Davis (1989), perceived critical mass, community identification, and perceived information quality were incorporated into the research model to explain the intention and usage of Wikipedia. This research is a work-in-progress and a questionnaire survey will be executed, targeting at Internet users who had prior experiences with knowledge seeking on Wikipedia.