In the mid-90s I taught a night class on Unix, and was experimenting with shell scripts from The Unix Programming Environment. There was an example using a loop and the who command to alert you when someone logged onto your local system. My cousin was a professor at a university several states away, and we had already figured out the talk command. So I decided to expand the examples in the book to use finger. By parsing the reply, somehow I could tell if my cousin was logged on, and I would send myself a notice. There was an ISP in the same building, and one day the ISP engineer came to visit me with a stern look. He asked, "By any chance are you sending a finger command every two minutes to this university's mainframe?" I proudly answered, "As a matter of fact, yes, I am!". I eagerly got out my Unix book to show him what I was doing. He just said, "Stop doing that. They have a system console logging program that has churned out dozens of pages of paper printouts because of you". I sheepishly acknowledged my mistake and quit running the script.