This paper examines the persistence and intensification of ignorance in the ostensible knowledge society. Given the ubiquity of ignorance, it focuses on research and observations dealing with functional knowledge deficits that challenge the ideal of the well-informed citizen. These developments are traced back to the contradictory dynamics of the knowledge society, specifically information explosions in the knowledge economy and the resultant knowledge-ignorance paradox. The theoretical unfolding of this paradox in terms of entry and speech barriers suggests that pockets of observed public knowledge - rather than ignorance - are exceptional and require specific explanation. While ignorance among individuals, as well as experts and organizations, is a serious social problem with potentially deadly consequences, ignorance remains relatively unrecognized since it has major liabilities as a marketable issue. The conclusion points to the importance of future research on the cultural and institutional production of ignorance.