While I’m not entirely convinced that one grain of won rice exactly corresponds to one grain of actual donated rice (who would bother counting the grains, anyway?), I am convinced that playing the game helps feed people.
At first I found it hard to believe too, how you can help charity without actually giving anyone any money. But it does make sense.
It’s the ads on the bottom of the page. Sponsors pay the site for having their ads there. Thus you generate money by being exposed to them, money that is then spent on the UN World Food Program.
Just getting your attention for a few seconds can pay for someone’s dinner. It’s at the same time an embarrassing indication of just how freaking rich we are here, and a great way to raise the standard of living elsewhere.