This week, the UN appealed for $562m for the victims of the Haiti earthquake. And that's just to cover the aid that will be needed over the next six months.
The good news is that more than that sum has already been pledged by governments, organisations and individuals across the world. The bad news is that after the immediate shock of the news coverage fades, a significant proportion of uncommitted pledges does not get donated. A year on from the 2004 tsunami, for instance, $550m worth of pledges still had not been paid.