It is not easy to kill something via USB as the plugs deal with all sorts of devices that are off spec but it can be done.  If you short ground and power the plug disables itself, TVS diodes prevent static electricity from damaging anything and excessive RF is bled off by the inline filtering beads.  That didn't stop this Hack a Day reader from figuring out a way to make a killer USB drive with a inverting DC-DC converter and capacitor bank.  The drive uses the power provided by the USB port to charge the capacitors to -110VDC which then discharges that to the data pins, enough to overcome the protection on the port and it repeats until the USB port is no longer capable of delivering power.  Considering many USB ports are integrated onto your CPU at this point, this is not a very nice thing to do; we present this as a warning and do not recommend this or similar projects be undertaken by our readers.

"[Dark Purple] recently heard a story about how someone stole a flash drive from a passenger on the subway. The thief plugged the flash drive into his computer and discovered that instead of containing any valuable data, it completely fried his computer. The fake flash drive apparently contained circuitry designed to break whatever computer it was plugged into."

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