Have you ever thought it was interesting how rare it is for an ATM to make a counting error? I’m always nervous I’ll be the exception. Will a bank just hand you a twenty if you go in and say “I told the ATM $100 but I only got $80? Uh, here, look at these four twenties it gave me?”

So many products and devices just don’t quite work, or fail frequently. Think about any consumer-grade piece of electronics. Or appliances. Or cars. We tolerate a certain rate of failure or deterioration. But it’s pretty neat that when we want to, and when the task is really important, we can design something that just works and keeps working. It depends, I guess, on how much cost we assign to failure...