Sure; that's more or less what I meant. Even calling attacks these bids by SIAI competitors to in fact offer better marginal-utility efficiency was a little over-dramatic on my part.

I have only one objection to the economic argument: "assume there is already sufficient diversification in improving or maintaining human progress; then you should only give to SIAI" is a simplification that only works if the majority aren't convinced by that argument. I guess there's practically speaking no danger of that happening.

In other words, SIAI's claim can only be plausible if they promise to adjust their allocation of effort to ensure some diversity, in the unlikely event that they end up receiving humongous amounts of money (and I'm sure they'll say that they will).

By the way, I don't mean to say that an individual diversifying their charitable spending, or for globally there to be diversity in charitable spending, is an end in itself. I just feel comforted that some of it is the kind that reduces overall risk (because the perceived-most-efficient group turns out to have a blind spot in retrospect due to politics, group-think, laziness, or any number of human weaknesses).