On a related note, it's always fun to demonstrate code's sensitivity to minor alterations to a non-technical person and see their reactions.

For example, just remove a semi-colon from a random PHP file that gets included in your web app and watch it completely die.

It's a decent way to impress upon people with little technical knowledge the importance of debugging.

(bonus points if you can create an impressive runtime bug that mangles the code's functionality in a flashy way, think mis-spelled variables in PHP)