Well, the marginal impact of a life-not-saved on the probability of a p-sing (can I call it that? What I really want is a convenient short-hand for "tiny incremental increase in the probability of a positive singularity.") probably goes down as more we put more effort into achieving a p-sing, but not significantly for the problem. The law of diminishing marginal returns gets you every time.

Let's not get to caught up in the numbers (which I do think are useful for considering a real trade-off). I don't know how likely a p-sing is, nor how much my efforts can contribute to one. I am interested in analysis of this question, but I don't think we can have high confidence in an prediction that goes out 20 years or more, especially if the situation requires the introduction of such world-shaping technologies as would lead up to a singularity. If everyone acts as I do, but we're massively wrong about how much impact our efforts have (which is likely), then we all waste enormous effort on nothing.