I strongly disagree. Whether it's existential risks or cryonics or Africa or whatever else it is you think near-optimally-useful charity would be focused on, the effect of a dollar going there outweighs the effect of making a random LessWronger a dollar richer by orders of magnitude. Given that we're talking about helping other people be more productive, this isn't an egoism vs altruism thing; it's a stupid altruism vs smart altruism thing.