Who has constant marginal utility of money up to $1,000,000,000?
Who has constant marginal utility of people up to 1000000000 people? (To answer the rhetorical question - no one.)
Consequences can't be inflated to make up for arbitrarily low probabilities. Consequences are connected: if averting human extinction by proliferation of morally valueless machinery is super valuable because of future generations, then the gains of averting human extinction by asteroids, or engineered diseases, will be on the same scale.
This reminds of of Jaynes and transformation groups - establish your prior based on transforms that leave you with the same problem. I find this makes short work of arbitrary assertions that want to be taken seriously.
Nick Szabo on acting on extremely long odds with claimed high payoffs:
Beware of what I call Pascal's scams: movements or belief systems that ask you to hope for or worry about very improbable outcomes that could have very large positive or negative consequences. (The name comes of course from the infinite-reward Wager proposed by Pascal: these days the large-but-finite versions are far more pernicious). Naive expected value reasoning implies that they are worth the effort: if the odds are 1 in 1,000 that I could win $1 billion, and I am risk and time neutral, then I should expend up to nearly $1 million dollars worth of effort to gain this boon. The problems with these beliefs tend to be at least threefold, all stemming from the general uncertainty, i.e. the poor information or lack of information, from which we abstracted the low probability estimate in the first place: because in the messy real world the low probability estimate is almost always due to low or poor evidence rather than being a lottery with well-defined odds.
Nick clarifies in the comments that he is indeed talking about singularitarians, including his GMU colleague Robin Hanson. This post appears to revisit a comment on an earlier post:
In other words, just because one comes up with quasi-plausible catastrophic scenarios does not put the burden of proof on the skeptics to debunk them or else cough up substantial funds to supposedly combat these alleged threats.