Questions and debate about Prototyping Prototyping, presentation by Chris Kelty, and Prototypes of Engagement: Trust, Transaction, and Digital Partnership, by James Leach, within the framework of the Prototyping Cultures: Social Experimentation, Do-It-Yourself Science and Beta-Knowledge seminar (November 4 and 5, 2010) at the Centro de Ciencias Humanas y Sociales (CSIC) and Medialab-Prado, respectively.