In order for a market to function efficiently, traders must be free to announce and describe their goods publicly and to bid prices. Such advertising is the primary means whereby buyers are informed about available goods; in some cases, advertising also informs sellers about available buyers. Although advertising is often regarded with distaste, without it buyers and sellers could exchange goods only if they serendipitously learned of each others' existence. Such a system would be a sham, hardly even identifiable as a "market" (i. e., a connected set of exchanges; cf. p. 4.5:15). Advertising is essential if consumers and producers are to maximize their utilities.

If advertising is restricted or censored, then the regulating authority must determine which advertising is permitted. That authority thus becomes in effect the ultimate dispenser of information. A true competitive market then no longer exists, since consumers are deprived of their primary means of obtaining objective information about the marketplace. One need not endorse all the viewpoints of specific advertisers to recognize the vital importance of free expression in this area ().