A growing body of work examines enterprise wikis. In this paper, we argue that “enterprise wiki” is a blanket term describing three different genres of wiki: single contributor wikis, group or team wikis, and internal-use encyclopedias emulating Wikipedia. Based on the results of a study of wiki usage in a multinational software company, we provide a taxonomy of enterprise wiki genres. We discuss emerging challenges specific to company-wide encyclopedias for which platforms such as Wikipedia provide surprisingly little guidance. These challenges include platform and content management decisions, territoriality, establishment of contribution norms, dispute resolution, and employee turnover.