With the Obama administration's focus on social enterprise as a means of solving some of our most pressing problems, the social entrepreneur has emerged as the chief change agent of our time. In this panel discussion, part of the Stanford 2009 Entrepreneurship Week, leaders of several vital organizations talk about the motivations, successes, and challenges associated with running a social enterprise. They consider what the economic downturn has meant to their missions, and they offer practical advice to aspiring entrepreneurs.