Trying a new online banking system today, I was impressed by their solid understanding of how to scare and frighten their users. If you go away from the browser window, do something else, and come back, you're told that you've been logged out due to inactivity or –they're not sure; how could they know? – "an illegal operation".
It's a good job they preface this with "Alert!" or it might not sound as serious as it obviously is.
"Illegal" is a word I'd definitely want to use if I were writing software for a bank. I suppose people writing software for hospitals don't talk about memory leaks; they have heap hemorrhages instead.