Holden Karnofsky on utility legions
Utilitarianism allows "utility monsters" and "utility legions." A large enough benefit to a single person (utility monster), or a benefit of any size to a sufficiently large set of persons (utility legion), can outweigh all other ethical considerations. Utility monsters seem (as far as I can tell) to be a mostly theoretical source of difficulty, but I think the idea of a "utility legion" - a large set of persons such that the opportunity to benefit them outweighs all other moral considerations - is the root cause of most of what's controversial and interesting about utilitarianism today, at least in the context of effective altruism.