At the philosophical heart of the freedoms of press and speech guaranteed by the U.S. Constitution is the so-called marketplace of ideas, in which it is assumed that a robust and unrestrained dialogue on significant issues is essential to public policy formation in a democracy. The media are assumed to have a particularly important role in this process, functioning as they do as essentially a fourth branch of government, and taking the lead in questioning the activities of the other three as well as those of other societal institutions.