"People don't like labels," says William H. Swatos Jr., who heads the Association for the Sociology of Religion. "And labels are hard to define anymore."
Most people involved with mega-churches admit some congregations swell their ranks with the entertaining Sunday show, feel-good sermons, and an appealing social environment, instead of focusing on the core religious message.
Experts, such as Thomas McElheny, whose company ChurchPlaza sells supplies and equipment to mega-churches around the country, insist that most do a good job of putting faith before entertainment.
Others are not so sure.
Randall Balmer, a professor of religion at Columbia University, compares some mega-churches with a giant chain store "that comes into a town and puts all the little stores out of business."
"We have lost members in our congregation to mega-churches in our town," says Randy Hammer, a pastor at the 100-member Grace Cumberland Presbyterian Church, in Franklin, Tenn.
With some — but not all — mega-churches, he thinks the medium takes precedence over the message.
"Their worship services are more productions than services."
He emphasizes there is an important role for mega-churches, but he also believes the strengths of small churches can be overshadowed by their larger neighbors.
There are some signs of a backlash against mega-churches — lawmakers outside Seattle are trying to impose restrictions on mega-church construction, for example — and some experts think that, eventually, mega-churches will be too big to keep up with the shifting tastes of American culture.
But for now, they are only getting bigger.