Unfortunately human error can never be completely eliminated. However, I'm not really talking about this type of problem. In my previous [1], the operator under

Unfortunately human error can never be completely eliminated. However, I'm not really talking about this type of problem. In my previous [1], the operator understood how the tool worked; they simply made a mistake when typing the command, and the tool without warning accepted the command to reboot the entire datacenter. Particularly telling are these comments: (sic) Operator-1: I ewas rebooting an rb Operator-1: forgot to put -n [...] Operator-5: [...] i've almost done what Operatolr-1 just did a *number* of times. That isn't a user understanding problem; it's a dangerous tool that doesn't fail safely. In your case, at least you detected the unusually destructive action and asked for verification. Youtube isn't even attempting simple sanity checks like your "N > 100" test. > normally makes you type the number > I just do not know how to make this more idiotproof Requiring explicit typing of the number or an explicit phrase like "Yes, I want to delete everything." are can help a lot. If possible, another good approach is to explicitly show the full list of proposed changes. Phrases like "This will change ALL of ..." might have multiple interpretations (ALL what? All of the the things in my entire account? All of the things in the current/last project/group? All of the things I think (perhaps incorrectly) were referenced in this action?). If someone is expecting to change only a few records, a confirmation popup that asks "Do you want to make these changes:" followed by a huge list has a large size/presence that should conflict with their expectations. "I only wanted to change a few things - wtf is this huge list?"