Douglas Adams, "Mostly Harmless"

A common mistake people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.

The last time anybody made a list of the top hundred character attributes of New Yorkers, common sense snuck in at number 79.

The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair.