Re: reasonable levels - You can have fail safe or fail secure. Those are two mutually exclusive options. Locking people out of content, whether it be consumers or a partner organization (like a theater) is the price of security (fail secure).
There is no condition where mild DRM is valuable to anyone. For consumers it constitutes a hurdle to use of content they have purchased without hindering non-purchased copies from being reproduced and distributed. No DRM allows the latter; unbreakable DRM ensures the former will be substantially affected at some point.