Well, not an atheist per se, but Anne Rice claims she is leaving Christianity. "“Today I quit being a Christian," she reportedly said. Now I, personally, have had trouble taking Rice's theology very seriously ever since reading Memnoch the Devil, but her argument seems to go something like this: Christ=good, Church=bad.
Personally it seem to me, as something of an outsider, that if you grock Christ, you are a Christian, and the church (or churches) out there really don't have to have anything to do with it. I suppose some members of some churches would disagree that you can get to Christ anyway but through them. But I see no reason to resign the field and let them win that argument.
If indeed this is what Rice is doing--rather than making one more grab for that elusive limelight.