Bill Day is a professor at New Orleans Baptist Theological Seminary and associate director of its Leavell Center for Evangelism and Church Health. His areas of specialization include evangelism and church growth.

Lizette Beard is project manager for LifeWay Research, where she has coordinated projects about megachurches and multisite churches. LifeWay is affiliated with the Southern Baptist Convention and is based in Nashville, Tenn.

Os Guinness is an author and social critic who lives in McLean, Va. His books include Dining With the Devil: The Megachurch Movement Flirts With Modernity. He is a senior fellow at the EastWest Institute in New York City.

Carl George is a church-growth consultant and coach who lives in Taylors, S.C.

Kimon Sargeant is vice president of human sciences at the John Templeton Foundation in West Conshohocken, Pa. Sargeant likens megachurches to shopping malls in his book Seeker Churches: Promoting Traditional Religion in a Nontraditional Way.

Robert Putnam is the Malkin Research Professor of Public Policy at Harvard University, where he studies civic connectedness, social capital, and religion and public life. He is author or co-author of more than a dozen books, including The Upswing: How America Came Together a Century Ago and How We Can Do It Again and Bowling […]

Irwin L. Morris is a professor in the department of government and politics at the University of Maryland at College Park. He co-authored an article titled “A Mighty Fortress: The Social and Economic Foundations of the American Megachurch Movement.”

John Vaughan is the founder of Church Growth Today, a research and consulting organization based in Bolivar, Mo. Its Megachurch Research Center has been studying U.S. and global megachurches since 1985. His books include Megachurches & America’s Cities: How Churches Grow.

Dave Travis is managing director of Leadership Network, a Dallas-based nonprofit organization that works to foster Christian leadership, innovation and church growth. Travis has advised pastors and other leaders of large churches throughout the U.S. and Canada. He is a co-author of Beyond Megachurch Myths: What We Can Learn From America’s Largest Churches (2007).