Private non-profit organizations are increasingly assuming key roles as human service providers within the new political economy. This paper aims to contribute to our understandings of how the participation of nonprofit intermediaries can modify the outcomes of the market and how such participation dynamically relates to policy and regulation. Developing an integrated approach to the question of sectoral difference and cross-sector collaboration, the paper focuses on the challenge of reform and sustainability in a particular social field - Workforce Development - situated at the intersection of law, market, and society. In an era of privatization, welfare-to-work reforms, and a "devolution revolution," government agencies must often decide whether to support and cooperate with for-profit or nonprofit intermediaries, and how to structure the relations between them. Often, through newly adopted voucher systems, the choice is left to individual consumers to decide between service providers that vary in organizational form. Focusing on the emerging roles of non-profits as they respond to the changing realities of work and service provision, the paper questions conventional assumptions about divisions between sectors. In particular, the paper analyzes a series of quantitative and qualitative studies on differences in performance among publicly funded vocational training providers. By comparing the complex circumstances in which nonprofit initiatives in a mixed industry produce interventionist and redistributional effects with those in which organizational form seems insignificant, the goal is to provide a better normative understanding of the comparative advantage of different organizational forms in changing social contexts.