At school, it was sort of a cat-and-mouse game between the students and the sysadmin. Kids would find new ways of evading the school blocks (different proxies, someone getting a bypass login, etc so they could access myspace) that the admin would then catch a couple weeks later and close. A lot of these proxies were distributed on the fileserver that was shared between students.
One day, I wrote a small piece of software in my programming class (in VB6!!) that would wait a random length of time, and then open and close the CD tray. I wrote a short batch script that would copy that file to startup and then open the current popular proxy software. I then changed the icon on that script and placed it where people expected to find the proxy software, giving them reason to run my script.
Students then unknowingly disseminated my software all over the school, and the next day (after PCs were rebooted overnight) the software would take effect and randomly open/close the CD trays of computers all over the school.
They ended up tracing it back to me (windows user permissions/ownership, probably) and I was promptly banned from computers at school through the end of the year and for most of the next.