http://news.yahoo.com/s/ap/20081022/ap_on_sc/sci_scotch_tape_surprise_2
No telling what they would have gotten from duct tape 
I'd imagine not much...the scotch tape effect depends in part on the corona effect on the tape material....which is what allows the formation of the plasma, and thus x-rays, during the rapid peeling.
Actually, instead of a poor man's X-ray tomography device, where this could come in handy is a low-power stealth communication system. would have to be low power, and only a few characters, like a decoder ring, pull the strip to generate plasma, run it through what would look like a tiny lighting arrestor in reverse....voila, one shot hard-to-find covert comms on a frequency band not currently being monitored by cryptologists, and too weak(probably) to be found by ELINT birds. I better hurry and file my patent.....
