Well, any delay to civilisation increases the probability that civilisation dies permanently, due to asteroid impacts or being unable to restart civiliseation because too many fossil fuels and other raw materials have been depleted.

You are quite right about the Pascal's wager nature of what I seem to be saying. To clarify, there are rationalists who's estimates are far higher than 10^-30 - some of them were actually planning how to dig in and keep the spark of civiliseation alive in a remote, well-fortified location for hundreds of years when the barbarians overrun the rest of the world (due to liberalism in general, not just homosexuality). I don't think you would start plans like that unless your prob estimates were a lot higher than 10^-30, because it implies that making those plans is a better use of your time than trying to save us from meteorites/AI/nanowar.