I can't tell you how many times I've seen our customers email us their username and password and say "I can't log in". Given that most people reuse passwords ...
On two occasions, I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question.