Abstract
Citizen science promises to include a wide constituency of participants in the knowledge production process, allowing lay people to make contributions based on their own expertise. In practice, however, the design of an infrastructure for citizen science may exert a filter on what counts as knowledge and impose standards for judging the quality and authenticity of contributions. This chapter explores the contrasts between top-down and bottom-up approaches in order to highlight some of the forms of exclusion that can occur in a knowledge infrastructure for citizen science, and to explore alternatives for designing infrastructures that more faithfully reflect lay understandings of knowledge.