It depends on the megachurch in question, and it's no different than, uh, microchurches.
Just speaking from my perspective working in a church--a large church, but hardly a megachurch...
I've gotten deep into the music side of things playing blended worship services for the last few years with increasing exposure to "progressive" worship. The question I have when it comes to music is whether the use of praise songs and choruses in worship really hits the mark for corporate worship or not. My conclusion is if you, as a congregant, only come to church for the rock concert or to hear the pipe organ, you aren't really meeting for worship. If your spiritual needs are the only needs you want met and you impose restrictions on everyone else along strict lines of your personal preferences such that you alienate worshipers who might be older or younger than you, then you might do better finding another church; else you need to pray and get back right with God because you're killing your church and future prospects of leading others to Christ.
I'm seeing a shift in the few megachurches I'm interested in from a contemporary praise and worship perspective. Yes, these churches and their worship teams have their own record labels and commercially release the music they use in their worship services. But I think it's more than just the money. I think once they figured out other people were listening to them and they garnered tremendous commercial success, they realized that writing and releasing music was more a service to the individual worshiper that could also enjoy use in other churches. So what I see are megachurches that are increasingly concerned with transforming the greater community of Christians by providing various services rather than selling an otherwise inaccessible product.
Almost 20 years ago, for example, commercial releases were tailored to feature worship leaders and artists. That basically meant if you were a male singer, you were expected to sing with a high tenor voice all the time. And it was good music. But the everyday schmo like myself (bass-baritone) who can't hit those screamin'-high notes is too embarrassed to even try singing along with that kind of worship leader, not to mention a worship leader pulling off that kind of thing in front of, say, a new church plant isn't going to be leading worship in that setting for long. In the last roughly 7 years, the commercial releases are more within a singable range for the average worshiper and are more accessible even to older crowds. You didn't really have this before the more recent megachurches took hold, and they've made some wonderful contributions to the world of progressive church music.
Sure, there's money in it, but that's beside the point. The money just allows them to continue to provide us smaller churches with amazing resources to help reach the local community. And it's not just music, but there are also the bible studies, Sunday school/small group curricula, and conferences.
And by megachurch, I think more along the lines of Gateway, New Life, North Point, and Hillsong. Some of my fave worship leaders/songwriters in the field are Jason Ingram, Reuben Morgan, Joel Houston, Darlene Zschech (did I mention I like Hillsong?), Paul Baloche, Chris Tomlin, Matt Redmond, and Kari Jobe.
Megachurch people I'm NOT into are pastors like Joel Osteen, Creflo Dollar, Benny Hinn, the Copelands, and others like them. I'm ambivalent towards Jimmy Swaggart and family, not that I'm theologically at odds with the Swaggarts, but more out of credibility issues. What I find fascinating is their musical direction--I mean, I respect his piano playing and he's a fine arranger as well as performing artist (at least if you like old-time southern gospel)--and that's just because that was the kind of music I grew up listening to and playing in church. What's also interesting is that I don't get the impression that it's all for the money. Yet I also find it distasteful when they ask for "gifts" to keep their broadcast ministry going Frances proudly proclaims who and how much someone sent via credit card. So I think it's wisest if you listen to someone like Swaggart, Bakker, or even Osteen to take their message with a grain of salt.
But as far as churches being inherently harmful because they're big churches? Nah... The kinds of ministries some of those churches provide are a tremendous help to the smaller churches, even those before their weekly attendance breaks 50. Heck, even Hillsong started out with 45 members meeting out of a public school. It's a MASSIVE church now with campuses across the globe. And I'm not saying they're 100% without reproach by any means, but they way they extend their reach to even the smaller local churches is impressive.