Malaria and Mosquitoes
Via Pharyngula, there may be a way to eliminate malaria, but the way to do it is to make mosquitoes healthier. Talk about a trade-off. Who knows what effect there would be to making the mosquito population healthier?
What if it were possible to eliminate mosquitoes completely. Would that be a good idea? Perhaps, but I assume there’d be a cost, maybe some birds or lizards or other (beneficial) insects might go extinct as well.