Financial control translates into levying ruinous dues or fees, or effectively hiring members and placing them on stipends or sales quotas. Consider the once-familiar image of Hare Krishna devotees selling books in airports. Or a friend of mine—today a respected officer with a nonprofit organization—who recalls how his departure from the Rev. Sun Myung Moon’s Unification Church was complicated by the problem of a massive hole in his résumé, reflecting the years he had financially committed himself to the church.

Problems with extremist leadership can be more difficult to spot. The most tragic cult of the last century was the Rev. Jim Jones’s Peoples Temple, which ended with mass murder and suicide in the jungles of Guyana in 1978. Only a few early observers understood Jones as dangerously erratic. Known for his racially diverse San Francisco congregation, Jones was widely feted on the local political scene in the 1970s. He was not some West Coast New Ager gone bad. He emerged instead from the mainstream Christian Church (Disciples of Christ) pulpit, which sometimes lent a reassuringly Middle-American tone to his sermons.

Yet every coercive religious group harbors one telltale trait: untoward secrecy.