Underground forums enable technical innovation among criminals as well as allow for specialization, thereby making cybercrime economically efficient. The success of these forums is contingent on collective action twixt a variety of stakeholders. What distinguishes sustainable forums from those that fail? We begin to address these questions by examining underground forums under an economic framework that has been used to prescribe institutional choices in other domains, such as fisheries and forests. This framework examines the sustainability of cybercrime forums given a self governance model for a common-pool resource. We analyze five distinct forums: AntiChat (AC), BadHackerZ (BH), BlackhatWorld (BW), Carders (CC), and L33tCrew (LC). Our analyses indicate that successful/sustainable forums: 1) have easy/cheap community monitoring, 2) show moderate increase in new members, 3) do not witness reduced connectivity as the network size increases, 4) limit privileged access, and 5) enforce bans or fines on offending members. We define success as forums demonstrating small world effect.