Purpose - To explore the challenges of worker ownership in complex and distributed collaborative production systems. Design/methodology/approach - Review of emerging developments in the organization of economic production and conceptual exploration of their implications for the ownership regime, and for worker ownership. Findings - Worker ownership research and advocacy usually take for granted what is to be owned: A factory or firm, exchanging on open markets. But this form of production, analyzed in the markets-hierarchy literature, is increasingly in question as more value is generated through flexible cross-boundary collaborations. As a result, the nature of ownership rights are contested from both within and without the business community. Practical implications - This paper explores some implications of these developments on employee ownership as a practical ideal: what are the main possibilities for the evolution of "ownership" rights in collaborative processes? Worker owners need to consider their relation to, and distribution of rights among, other collaborative partners, including knowledge contributors and interdependent stakeholders. Social implications - Implies a need to move beyond markets-hierarchies frameworks, in which concern is focused on the governance of firms, to building a set of mechanisms for the organization and governance of production networks. Originality/value - Poses a set of problems for the worker ownership field emerging from the changing nature of production and organization.