mrnick writes: "Eric Simons, 19 years old, was working at incubator, Imagine K2, in Silicon Valley and when his grant money ran out he moved into the office. He slept on a couch, took showers and washed clothes in the office gym, and ate for free in the cafeteria all the while working on his new start-up. He was able to get away with this for two months before being discovered by security guard." Link to Original Source
Computers are unreliable, but humans are even more unreliable.
Any system which depends on human reliability is unreliable.