[knowknowledge]

I've heard the aphorism before, but the reason I like this interpretation is that it mentions that "even technical people" make mistakes. I usually take this quote to imply that the people using your products are getting dumber, but here the implication is that as people are getting smarter they'll test your products in ways that you weren't smart enough to think of first. The products need to be safe from the smartest users, not just the dumbest users.