It is easy to forget that, for centuries, most people were unaware that they had any choice in religious matters. They were surrounded by people like themselves, and only a few ever met believers from other traditions. No more. A mosque is being built around the corner and, look, the Dalai Lama is on tv again. Thousands of religious and spiritual chat rooms and blogs have popped up. This is the age not only of the “cafeteria Catholic,” but also of the cafeteria Buddhist, Baptist, and Mormon. More and more people view the world’s religious traditions as a buffet from which they can pick and choose.

In this environment, religious hierarchy is crumbling fast. The notions of consumer choice and local control have stormed the religious realm, and decentralization of faith is now the order of the day. Religious leaders who once could command, instruct, and expel now must cajole, persuade, and compete.

Protestant Christians, of course, have always been suspicious of hierarchy as a matter of principle. In practice, however, they have often let church bureaucrats run their affairs. Today, local Methodist or Lutheran congregations often ignore the dicta of church leaders, and denominational “brand loyalty” is a thing of the past. The 77 million-member Anglican Communion recently faced a schism over the ordination of a gay bishop. In response, the Archbishop of Canterbury could only try to encourage a dialogue between the feuding parties; a resolution of the crisis from on high was out of the question.

Christians are not the only ones straining against the religious hierarchies of old. In the early 1990s, the entire organized lay wing of Nicheren, the largest Buddhist organization in Japan, effectively seceded, leaving behind a rump priesthood without parishioners. Although a...