Leadership plays a central role in the success of many forms of online creative collaboration, yet little is known about the challenges leaders must manage. In this paper, we report on a qualitative study of leadership in three online communities whose members collaborate over the Internet to create computer-animated movies called "collabs." Our results indicate that most collabs fail. Collab leaders face two major challenges. First, leaders must design collaborative projects. Second, leaders must manage artists during the collab production process. We contrast these challenges with the available empirical research on leadership in opensource software and Wikipedia, identifying four themes: originality, completion, subjectivity, and ownership. We conclude with broader implications for online creative collaboration in its many forms. ACM Classification Keywords H.5.3 Group and Organization Interfaces---computersupported cooperative work, collaborative computing. General Terms...