There's a quote about this:

Perfect is the enemy of good.

Commonly attributed to Voltaire

Upvoted simply because Less Wrong is seriously lacking in discussion of Schelling points and how they're critical components of the way humans think about practical problems.

I do think your hypothesis is plausible, but the reasoning it describes seems too complex. One would think like that only if one cares about being consistent and reflects on that, and only after one has decided that the "I've done my part of the job" excuse is not enough... and it seems improbable that most people think like that.

Also, it seems to me that "help Haiti just this once" is not the same scenario as "help just this person".

Worth testing, though. I guess if you set up a scenario like "Help poor kid X grow up well", a long term goal with kinda-hard-to-predict cost that most people wouldn't be willing to pay all at once, with a specific identifiable subject...

If we're told we need to donate to save "baby Jessica", it's very easy to donate exactly as much money as is necessary to help save baby Jessica and then stop.

I have the impression that identifiable cases tend to get far more money than what'd be needed to save them.

It sucks how sometimes I notice a way in which I could be more effective, but don't do anything because I could've in theory done something a long time ago.

Very solid point, and I appreciate it - I immediately identify with it as one of the major reasons I tend not to engage in charitable giving myself, except for those rare occasions where a charity I support is requesting a specific (and small) amount...

So part of what I think is going on here is that giving to statistical charity is a slippery slope. There is no one number that it's consistent to give: if I give $10 to fight malaria, one could reasonably ask why I didn't give $100; if I give $100, why not $1000; and if $1000, why not every spare cent I make? Usually when we're on a slippery slope like this, we look for a Schelling point, but there are only two good Schelling points here: zero and every spare cent for the rest of your life. Since most people won't donate every spare cent, they stick to "zero". I first realized this when I thought about why I so liked Giving What We Can's philosophy of donating 10% of what you make; it's a powerful suggestion because it provides some number between 0 and 100 which you can reach and then feel good about yourself.

There's another option which I think may be better for some people (but I don't know because it hasn't been much explored). One can stagger one's donations over time (say, on a quarterly basis) and alter the amount that one gives according to how one feels about donating based on the feeling of past donations. It seems like this may maximize the amount that one gives locally subject to the constraint of avoiding moral burnout.

If one feels uncomfortable with the amount that one is donating because it's interfering with one's lifestyle one can taper off. On the flip side I've found that donating gives the same pleasure that buying something does: a sense of empowerment. Buying a new garment that one realistically isn't going to wear or a book that one realistically isn't going to read feels good, but probably not as good as donating. This is a pressure toward donating more.

This seems very plausible to me.