I consider giving small amounts ($25-50) to a number of different people in developing countries to be nearly the least I can do to help those not as lucky as I am. I am a bit disheartened by some of the cynicism of this thread.
I aim to keep a fixed amount in Kiva, cycling funds to bump my spend a little. That amount only increases if I think I can absorb a total loss of the funds, even if that's basically never going to happen. Spread your risk by country, lender and type of project and it's a low risk activity.