Any real-world security system is inherently complex. Making them safe and secure is hard. Controlgeek Blog has an interesting pointer and summary on on a very interesting white paper How Complex Systems Fail. I also found his paper, which is only a few pages long, a fascinating read (like John Huntington and Schneier on Security). If you feel that systems take on a life of their own once assembled, you will find this few pages long paper interesting read.
Besides engineers who design complex systems also security professional should read it. It’s not directly about security, but it’s all fundamentally about security. Humans are always in the loop somewhere (input or output or in the middle somewhere) and are the inescapable root cause of failure.