Really. You'd need military-grade security and strictly planned access levels -- and then look at what Snowden did.
Even more, in most companies there's just no way to implement this. Data is just what they're working with and often the most basic security is bypassed or never implemented just because it's too bothersome while being without any immediately visible gain.
Come on, every admin out there will know that just too well. Security against attacks from the outside, yes. Security against attacks from the inside? Forget it. People need to work with the data and even just to make sure that people have only the access they really need often is so much bother that nobody wants to start with that.