Gawker recently published an essay arguing that we are all under a moral obligation to maximize population growth. The piece is receiving an unusual amount of attention, owing to the fact that it was originally commissioned by Vox, which then declined to publish it.
One might wonder why anyone would believe that we humans as a whole, or any individual pair of us, were under an obligation to produce as many more humans as possible, even if it were true that more humans meant more total happiness (all problems about future persons, and adding up happiness across persons, laid entirely to one side). I think I finally landed on the answer. Let's all agree that human lives have value, and happier ones are better. But what does it mean for anything to have value? Imagine God (or the cosmos, if you prefer) as a grand consumer. What he/she/it consumes are complete human lives. A happier human life is a higher quality - more preferred - consumption good than a less happy one. So sets of human lives, of varying qualities, are bundles of commodities - commodity vectors in an n-dimensional commodity space. Our grand consumer, being economically "rational", will prefer a bundle of low quality lives to a bundle of high quality ones, so long as the number of lives in the former is sufficiently greater than the number of lives in the latter. (Alright, strictly speaking, our commodity vectors all contain n lives - a 'smaller' one has more places occupied by zeroes than a 'larger' one.) And who are we, mere humans, to argue with that grand consumer preference? What should we do, after all, but comply with the dictates of the universal market, and produce what it demands? And the more we produce, the more is consumed, the happier he/she/it is - the better, the more valuable the universe is.
It is not a coincidence that Utilitarianism developed in the same time and place as vulgar political economy - i.e. marginalism. Schumpeter keenly saw that JS Mill, though himself a classical economist, developed a philosophical system which prefigured the foundations of Marshall's economic theory.
And, one can only hope, this sort of thing lets us see the justice in Marx's description of Bentham as "a genius by way of bourgeois stupidity." At the very least, the fact that this argument is taken so seriously by so many serious people, who nonetheless appear to have no clue as to what actually motivates it, is a vivid confirmation of the hidden influence of the social relations of production on the world of ideas, and the development of what counts as knowledge.