Economist blogger M.S. (sorry, unfortunate initials) says, in an article about the growing influence of the Chinese and Russian states, that he doesn't "believe the phrase 'free-riding on American military power' describes any actual countries in the world in the year 2010."
MS need only imagine a world sans-U.S. and wonder whether other countries' military might might (hee hee) put any American allies at risk. Would MS really expect the major powers of the world to be so, er, peaceful, if not for the deterrence caused by American military presence -- and its willingness to get involved?
Now I won't counter MS's absolutism by spouting my own absolutism about military "free riding" in 2010. As a matter of historical fact, Europe and Japan have been able to devote less of their economies to defense because of their post-WWII alliances with the U.S. But today, who can be sure whether they're still free riding? It might be that the international economic interconnectedness that developed in the war's aftermath was more responsible for the reluctance of major powers to attack their neighbors than nuclear deterrence. There's just no way to experiment -- maybe China and Russia and the nations of the Middle East would just be pacifist buddies to Europe and Japan. It's possible. But I don't share MS's conviction.