The rapid erosion of privacy poses numerous puzzles. Why is it occurring, and why do people care about it? This paper proposes an explanation for many of these puzzles in terms of the increasing importance of price discrimination. Privacy appears to be declining largely in order to facilitate di®erential pricing, which o®ers greater social and economic gains than auctions or shopping agents. The thesis of this paper is that what really motivates commercial organizations (even though they often do not realize it clearly themselves) is the growing incentive to price discriminate, coupled with the increasing ability to price discriminate. It is the same incentive that has.