So, let me ask you this. Say we have two completely separate areas - for the sake of argument, we'll have the Earth and a separate planet in our solar system called Earth Mk II. For the purposes of this thought experiment, the two planets are totally hidden from each other in such a way that neither will ever discover the other, and nothing that happens on one will ever affect the other. Earth and Earth Mk II are pretty similar places, with equal populations. The big difference is that Earth has 90 units of happiness averaged throughout the population, and Earth Mk 2. has 98. Now, even though they're completely separated, isn't the correct move in average utilitarianism to destroy Earth, so that the solar system has a higher average happiness? Further, assuming we can do this without affecting their happiness, isn't the correct play for average utilitarianism simply to find the happiest being in the universe, and kill everything else? That conclusion seems a little repugnant, too.