the article I read about the $100 computers said that it would be used mainly for educating children even in the U.S. The children that were mentioned in the article were from all across the world who have been having an education. This computer is an educational tool for those kids.
putting computers in the classroom has FAILED to improve the U.S. education system. kids use computers for chatting, games, mp3's and copying and pasting homework and papers.. you can stick a a whole set of enyclopedias in a classroom, don't mean kids gonna read it. you can build a whole library next door, don't mean kids ever gonna go afterschool. imho, this is a money making venture covered up by pseudo humanitarian intentions. or even worse, some left wing dream of a perfect world. "imagine all the people..."
I don't think the computers will make a difference at first in the hands of people who face famine, at least not at first. However, where it will make a difference in the 3rd world will be to promote freer flow of information, access to outside ideas, which will hopefully promote democracy and help enforce property rights (starting in the urban centers, and spreading outward). This will increase the productivity of poor nations and ultimately help prevent the conditions leading to famine. Maybe hopelessly optimistic but availability of cheap computers is better than no access to them at all.