Make a real private function is not a good reason to reduce maintainability and testability to me. It's a lack of javascript language and IMO the simplest way in object literal is using leading underline character or at least having a closure and having at least inner functions as possible in a simple module. Though each module is born as a small once but in the long run as the features/fixes grow, the amount of private functions are killing us on debugging, __WindowManager__ and __SoundManager__ are both good examples.

How do you think? If you still disagree, please try to find another reviewer and convince him.