The Touch naturally would not be a good candidate for ziplock baggie, because of it IR touch screen. Just tested on the Paperwhite, and there it works with no problem thanks to the capacitive touch screen. The screen still responds very precisely and accurate - swiping might be a bit complicated to do wrinkle free, though. Don't have a beach to try it out here, but in essence it should work. The thin layer of baggie makes it just a tiny bit harder to get a response, but that is almost not noticeable.
p.s.: I did stick my Touch in the baggie after playing with PW, and the results were horrible - the baggie itself can activate the screen. It clearly is not as see-through as it may appear (pun intended) - at least for the IR sensors.