My job over the last thirteen years as a penetration tester has given me a unique understanding of security from an attacker's point of view. I have conducted hundreds of penetration tests on organizations ranging from Federal government nuclear weapons labs, to banks, city governments, and practically everything in between. I know what makes an attacker's job easy, and what makes it difficult or practically impossible. I am oftentimes surprised that in 2014, I can gain access to one server or workstation, and use it to traverse the entire network, unhindered at the network layer.
I'm shocked that close-circuit television (CCTV) systems, alarm systems, building access control systems, and manufacturing process control systems are just "hanging out" on the corporate network for all to see. I recently conducted an assessment on a very large city. They had a flat and permissive internal network, meaning there were virtually no barriers between their different systems.