If Barack Obama backs down, he will be greatly criticized for being "weak" and for having been beaten by Vladimir Putin once again.  If Putin backs down, he will be greatly criticized for being "weak" and for abandoning the Russians that live in Crimea.  In essence, Obama and Putin find themselves trapped in a macho game of "chicken" and critics on both sides stand ready to pounce on the one who backs down.  But this is not just an innocent game of "chicken" from a fifties movie.  This is the real deal, and if nobody backs down the entire world will pay the price.