According to the local paper today, New Life has something like 1,000(!!) small groups. It's not for me, but I know a number of folks who go there, and it does feed them.
I don't know how a megachurch can be effective without having small groups.
A visiting pastor was speaking at my church in August and he about had us on the floor laughing about an experience he had in his early days in the ministry. He wanted an answer to prayer that wasn't what God wanted for him but he didn't know that at the time. He said he'd heard about Pastor Cho having this "prayer mountain" so he got on the Internet and Emailed them his prayer request. He said he didn't know what he'd set loose. He said, "God only knows how many millions of Koreans started praying for me, and not for what *I* thought I needed!" In the end, the pastor got an amazing series of answers, and his initial request fell by the wayside. He laughs about it now. So did we. Makes me smile just remembering it.
It isn't the megachurch that is not right. It's when an individual leader isn't walking in righteousness that things get not right.