In a paper entitled "Nothing happens in the Universe of the Everett Interpretation": http://arxiv.org/abs/1210.8447 Jan-Markus Schwindt has presented an impressive argument against the many-world interpretation of quantum mechanics. The argument he presents is not new, but, in my opinion, nobody ever presented this argument so clearly. In a nutshell, the argument is this: To define separate worlds of MWI, one needs a preferred basis, which is an old well-known problem of MWI. In modern literature, one often finds the claim that the basis problem is solved by decoherence. What J-M Schwindt points out is that decoherence is not enough. Namely, decoherence solves the basis problem only if it is already known how to split the system into subsystems (typically, the measured system and the environment). But if the state in the Hilbert space is all what exists, then such a split is not unique. Therefore, MWI claiming that state in the Hilbert space is all what exists cannot resolve the basis problem, and thus cannot define separate worlds. Period! One needs some additional structure not present in the states of the Hilbert space themselves. As reasonable possibilities for the additional structure, he mentions observers of the Copenhagen interpretation, particles of the Bohmian interpretation, and the possibility that quantum mechanics is not fundamental at all.