i've never powdered my tubes, and i don't get what the big deal is. according to some, a layer of talc between the tube and tire will help air escape if the tube is punctured... it could turn a slow leak into a fast leak. a few months ago a tiny shard of glass worked through my marathon/kevlar front tire, and i was able to make it home after pumping up the tire before i got on the bike, and pumping again about halfway home. if that was a fast leak, i would have torn up a second tube on the way home because the glass was well hidden in the tire.