Randall W. Harding sang in the choir at Crossroads Christian Church in Corona, Calif., and donated part of his conspicuous wealth to its ministries. In his business dealings, he underscored his faith by naming his investment firm JTL, or "Just the Lord." Pastors and churchgoers alike entrusted their money to him.

By the time Harding was unmasked as a fraud, he and his partners had stolen more than $50 million from their clients, and Crossroads became yet another cautionary tale in what investigators say is a worsening problem plaguing the nation's churches.

Billions of dollars has been stolen in religion-related fraud in recent years, according to the North American Securities Administrators Association, a group of state officials who work to protect investors.