> As far as malaria is concerned, DDT turns out to be real effective at killing mosquitoes, the major problem in the developing world of LOTS of infectious diseases. But those of us in the developed world got more concerned with the eagles and stuff and essentially go out of our way to keep DDT from being used even though it's use in the developing world would literally save tens of thousands of human lives.
In many impoverished areas it is largely ineffective as a mosquito pesticide now. If we'd use it more liberally, it's possible that resistance would have developed more quickly due to the increased selection pressure. DDT is not a silver bullet.
Mosquitos have developed DDT resistance: http://en.wikipedia.org/wiki/DDT#Mosquito_resistance
In many impoverished areas it is largely ineffective as a mosquito pesticide now. If we'd use it more liberally, it's possible that resistance would have developed more quickly due to the increased selection pressure. DDT is not a silver bullet.