I was always taught to design systems to be as idiot proof as possible, because the further an error gets into a system the more difficult and costly it is to correct it.
The most memorable quote I remember about "idiot proof" was
something from the early days of the automobile, in reference
to the methods of changing gears. Something along the lines
of "It is impossible to design a foolproof gear change mechanism
because fools are so ingenius" They will find a way...