I came into work today and found my computer booting over and over again, with that annoying screen that Macs do that says "Something's gone wrong. Press a key or wait" in multiple languages, only to wait or press a key only to have the kernel panic again.
So how was it done? Purely by accident would you believe, just a rather unfortunate one. After I left and before I arrived the next morning, someone else had used the room. Upon clearing the desk, someone placed a glockenspiel bar across the top of the unit and rested a condenser microphone across the back plate and the USB port area, which is where the FSB would be stored in a Mac.
Let's look at these items. The note wouldn't pose a problem; although it IS metal, it wouldn't hold much of a charge, nor does it get anywhere in contact with electric equipment. Unlike the microphone however, which is laced with electric circuits and a massive, massive magnet. It may not be as strong as some of the internal magnets in say a hard disk drive, yet keeping it across a running Mac Mini would depolarise any electrical currents in the vacinity, causing major damage.
In brief, the disk controller, the FSB and a lot of peripherals like the disk itself, maybe the RAM and perhaps even any connected USB device (who knows) are in danger of damage. Over a ten or so hour period, that's what happened.
Rather an expensive accident, but I am amazed that no more danage than that was caused!