Here I propose a VERY SIMPLE and intuitive argument that MWI, with its MINIMAL set of assumptions, cannot explain the Born rule. The argument goes: The minimal set of assumptions defining MWI is: 1. Psi is a solution of a linear deterministic equation. 2. Psi represents an objectively real entity. Assume that the Born rule can be derived from the assumptions above. Then ANY system satisfying these assumptions must necessarily have the probabilistic interpretation defined by the Born rule. Therefore, in order to show that the Born rule cannot be derived from the assumptions above, it is sufficient to find one counterexample of a system that satisfies these assumptions but does not have the probabilistic interpretation. And it is very easy to find such an example; just take some appropriate wave equation from CLASSICAL mechanics of fluids. Q.E.D. Of course, this is just a rough idea for the argument. I'm sure it can be further refined, e.g. by replacing 1. above with something more specific and yet sufficiently general. Since the idea is so simple, I'm sure that many readers of this can contribute to further developments of the idea. Any suggestions? Comments? Objections?