At the end of the eighties I was working for a company that made software for doctor's offices. I frequently gave demonstrations to small groups of physicians. One of the main concerns was safety. There was so much talk about hackers. Would their patient records be safe from intruders? I explained to them that one could only get into a computer from outside the office if the modem was on, and the computer was running a communication program and acting as a host. At that time, this was a rare situation in private practice. But even the most powerful argument I could think of, "You can't break into a computer that's turned off," did not have the impact I had hoped for. One way or the other they were convinced that a clever hacker would not be stopped by such a trivial problem!