How to participate in development?

A friend writes (paraphrasing and some editing)...
Michael, it is the old retail vs wholesale question. If you are Bill Gates, you think big picture. If you have $1000 to give, you take on a precise project. I took a generator to Rwanda in 1994 for an orphanage; very fulfilling project. Big help to them...If my friend and I have say, $25,000 to spend on Darfur, how should we spend it? Give to Oxfam for village aid on the Chad border, give to African Union for troops, give to Save Darfur divestiture campaign, give to lobbying to pressure US to aid a military intervention, enforce a no military-fly zone over Darfur. (It is funny that we are appealing to the US govt. like it is so limited a power, like France, not the world's superpower. Nick K's reports from Rwanda are most informing to me.) The world, UN does not want to take over running Darfur like it has in Kosovo.

I think there are limits to the big change model: you get a model project funded, then if successful, you apply it to the big picture. When you know the big picture problems are so overwhelming, is it good faith to embark on a Sach's-like project, which by the way a Harper's article a few months ago (for subscribers only; a free description is here) was very critical of in Kenya, knowing that you cannot get funding for big picture. Is it then enough to say, "Oh, we tried." I don't have the answer here, just concerns.