The literature on teacher leadership tends to omit mention of the dark side of leadership. This is troubling since, after all, examples of bad leaders come readily to mind. This paper delves into the literature on bad leadership, illuminating it with reference to Iris Murdoch's moral psychology, to elaborate an explanation as to why leaders often go bad. This framework is then applied to teacher leadership in order to lay out certain ethical and educational risks associated with the indiscriminate promotion of teacher leadership, as well as concerns related to the theme of social change. The paper concludes that we should be careful if we decide to promote teacher leadership, lest such efforts lead to the proliferation of bad leaders.