It is only necessary to give up to the point where the problem is fixed. If everyone giving all their surplus would be non-optimal, there is some amount less than "all" for each person to give that would be optimal. However, most people are not giving anywhere near this amount, so in the here and now the world will be better if you give all your surplus. If the world were different, the principles that led to this advice would lead to different advice that would be optimal in that situation.
My entire point was that the problem cannot be fixed in this way. Pouring money into a region that doesn't have a functioning economy doesn't create an economy, in fact it may even make a self-sustainable economy impossible. Meanwhile, it takes money out of an economy that is functioning which amounts to a net loss to world productivity.
I'd be really interested to hear what the Less Wrong community thinks of this. Don't spoil it by reading the comments first.
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