I have been showing students the above as a lesson in both:
1. Computer security. Reminding them not to forget to logout: “its not just your email and files at risk it’s your Facebook account”.
2. Testing systems is important. People will do the silliest things. If you ask someone to enter their age, don’t assume it will be a number, they could answer “sixteen” . For closely typed languages a string instead of a number can produce a run time error if not handled correctly by their program.