Ouch. I'd thought of the malware risk of plugging into a dead drop, but it never quite crossed my mind that someone could basically turn one into the equivalent of the Etherkiller:
I suspect some hubs would be suitable for buffering against that sort of attack. Not sure which though, or whether a more subtle approach (some sort of pulsed power to avoid tripping polyfuses, perhaps) would still be practical.
If you wanted to be a dick, I think replacing the insides of a USB stick with a large charged capacitor and leaving them in parking lots would be the way to go.
http://www.fiftythree.org/etherkiller/