The Political Compass is silly. Just try taking it and try providing what is clearly the "right" answer to each question. I just did so and came out almost all the way to the left and libertarian. Hmmmmmmmmmmmmmm...now what does that say about the author of the quiz?
It's a good idea, but I think it's impossible to pull off in practice, at least not when there's only one person involved in picking the questions and deciding what the answers mean about a person's political views.