The Ted Haggard case calls attention to an important issue addressed in this Associated Press article: US evangelist sex scandal raises questions about 'superstar' megachurch pastors. I myself have never been an enthusiast for independent church congregations, especially of the "megachurch" variety. There is something unhealthy about a huge congregation revolving so heavily around one person's ministry. There is often little oversight, and certainly not from outside the congregation, since there is no denominational machinery that might provide it. At its worst this sort of arrangement can produce a cult of personality. However, I think the second statement below is not entirely accurate:
Nearly all megachurches are independent from a denomination — an asset for their flexibility, but a liability when it comes to checks on power. By contrast, mainline Protestant denominations vet clergy credentials and have elaborate systems of church tribunals, similar to civil courts, that discipline errant ministers.
I do not know what the word errant is intended to convey here, but the larger protestant denominations have mostly given up on the idea of doctrinal error, even in their own leadership. The Anglican Church of Canada, as just one example, has no means of reining in a rogue bishop. The irony is compounded when one considers that the Greek word επίσκοπος (bishop) literally means overseer, thus raising that ancient question of who will oversee the overseers. Unfortunately the Anglican Church has not answered this adequately in its own ecclesiastical polity.