I can see following that for charities with high-probability results; I would certainly support that with respect to deciding whether to give to an African food charity versus an Asian food charity, for instance. But for something like existential risk, if there are two charities that I believe each have a 1% chance of working and an arbitrarily high, roughly equal payoff, then it seems I should want both invested in. I might pick one and then hope someone else picks the other, but it seems equivalent if not better to just give equal money to both, to hedge my bets.