Matt Chandler spoke about the de-churched a couple of weeks ago at Advance09. He said that many Christians put God in their debt. They do a lot of good things and get really angry when something doesn't go well for them. So they walk away from God and that's how we get the de-churched. As he was speaking then, and watching this clip again now, I painfully recall a close friend who is no longer walking with the Lord, I believe for this very reason. Let us remember that it is only by His unmerited grace through Christ that we able to walk with and be loved by Him.
Here's the clip: