@maporsche,
I was in the Army. I was only a lowly NCO, but my first MOS (military occupational specialty, a.k.a. my job) was 29Y - Satcom repairer. It required a top secret clearance. Long story short, my admittedly limited experience with the US government's general handling of classified correspondence was that it was haphazard. The dawning of digital email, while it may have seemed to be the perfect way to streamline and organize, wasn't handled much better. Maybe it got miraculously better when Clinton was in the state department, but I seriously doubt it. What do I mean by haphazard? Two things jumped out at me. There were far too many documents marked 'classified' that didn't need to be. And they gave too many people 'secret' and 'top secret' clearances.
For this reason, it is FAR easier for me to believe that Clinton was "careless" in her handling of classified information - simply because, for all their blustering, the US federal government produces some of the biggest cluster-**** bureaucracies ever, and their documentation reflects it.
It's easier to believe that, than... What is it exactly they are accusing her of? I don't think they even know. I don't think they are saying she intentionally shared classified materials with unauthorized individuals (like Petraeus did). They make so much noise and spend so much money and time, but what crime have they actually accused her of?