A similar point is made in Gene Weingarten's "Fatal Distraction" (http://www.pulitzer.org/works/2010-Feature-Writing http://www.pulitzer.org/works/2010-Feature-

A similar point is made in Gene Weingarten's "Fatal Distraction" (http://www.pulitzer.org/works/2010-Feature-Writing http://www.pulitzer.org/works/2010-Feature-Writing), which was about parents who forget a child in the car. Excerpt: "[British psychologist James Reason] likens the layers to slices of Swiss cheese, piled upon each other, five or six deep. The holes represent small, potentially insignificant weaknesses. Things will totally collapse only rarely, he says, but when they do, it is by coincidence -- when all the holes happen to align so that there is a breach through the entire system."