Right, that makes sense, thanks. To clarify, I don't actually think anyone will be put off taking the survey because of this. I will definitely be taking it anyway :)
Regarding the $500 "prize":
I've seen this sort of prize for a few things recently. I don't really understand how it's supposed to incentivise me to complete the survey. The total money donated is $500 regardless of how many complete the survey, so unless I think that I'm at least as well informed than the average respondent about where this money should go (which I definitely don't!) then if anything, isn't it an incentive to not complete the survey?
I feel like you're probably too sceptical about the possibility of us ever knowing if longtermist interventions are positive. You say we can't get feedback on longtermist interventions, and that is certainly true, but presumably later generations will be able to evaluate our current long-termist efforts and determine if they were good or not. Or do you doubt this as well?
I've sometimes wondered about this, but I'm not sure how it gets past the objection to Response 1. In 1000 years' time, people will (at best!) be able to measure what the 1000-year effects were of our actions today. But aren't we still completely clueless as to what the long-term effects of those actions are?