My favorite hypothesis for consciousness skepticism is the "colorblindness" theory (advocated by one of Yvain's old profs, apparently). That is, just as some people cannot tell red from green, some people have a hard time with qualia.

Under this hypothesis, there are observable ramifications of a lack of (or difficulty with) qualia. Folks who have difficulty with qualia actually write about consciousness differently from folks with qualia. If you have qualia, you write like Chalmers. If you don't, you write like Dennett (or the grandparent) :).