Then how about we take the human brain's inability to multiply into account? Above a certain number of people, the brain goes numb to any increments, in suffering or otherwise. Then it wouldn't matter if you're 3^^^3, 3 million, or even 3 thousand; anything past a certain limit is just background noise, statistics.
Which I suppose would have an interesting effect on the value of genocides and other mass-scales inflictions of suffering, and donation management and other mass-scales alleviations of such. I guess what really matters is the tangible result to you, those close to you whom you care about, and the more immediate social environment you move in.
You'd care about the state of a neighborhood, not because you care about any of them individually; you don't even know them. No, you just want to walk around happy people so you can feel happy yourself. Depressed people are depressing. A utilitarian, linear calculation of wealth increase (or even one that'd include a law of diminishing returns) is simply a very rough approximation towards this goal of seeing smiling faces.
And then there's of course the matter of satisfying your values, which has much more to do with the state of your mind than with that of others'.
And this is the limit of my working memory for today. I'll go mull this over... Of course, I suppose I'm hardly being original here; could you point me to sources that have already thought over all this? I'd hate to find out I'm wasting brain-time reinventing the wheel.
I have never been on a Lesswrong meetup because they tend to take place too far away from my range in terms of distance and budget. Because of that, I don't know if those perform this function to everyone's satisfaction in such a way that what I'm suggesting here doesn't seem worth the effort. I hear that they're a lot of fun, and involve quite a bit of silliness, though; I find those cruelly lacking on Lesswrong proper, whether it be in main posts or discussion posts, and their relevant threads.
That's why I think it would be nice to have a forum, a place to have normal discussions, where you don't have to watch that you don't say anything stupid or out-of-line lest you unexpectedly lose karma. A place to exchange jokes, frivolities, and entertainment. A place to talk about stuff that isn't rationality or singularity-related. A place to relax and enjoy the company of like-minded folks. A place to take a more personal approach to communication, with sequential rather than branching conversations. A place to make and be friends.
Don't you think having that would be nice?
EDIT: Also, if this place does already exist and I'm not aware of it, I humbly request that you provide me a link, for which I would be most grateful.