I notice that you kept referring to the 'private sector' in your posting. I have to say, in our defense, that the private sector is leaps and bounds ahead of government and military in terms of infosec as far as I have seen. If ever there was an organization with the resources to really attack and deal with information security, it's the U.S. Government and it' s military. I don't know what excuse they could offer up. Unix is evil.
Daemons run wild.
Zombies roam and children are killed. Actually, the defense in depth angle is right out of the Pentagon's most recent play book. The problem is that all denfensive strategies will ultimately fail if here is no offensive component to your campaign. You cannot win a war with defense. In IT, even with the best thought out defensive techniques there is a good chance that if you are a popular target of opportunity you will be compromised.