There was an article on this the other day. Apparently, scientists used zinc finger nuclease to delete the gene in mosquitoes that allow mosquitoes to digest blood. So the mosquitoes died of starvation.
I'm not sure how ZFNs are meant to be used, but I guess this could be one of their benefits- no more mosquitoes. It could help us wipe out some horrible diseases that mosquitoes love to pass on like malaria. How it would impact the ecosystem is another issue tough. I guess we still need to do some more research before we really put ZFNs to use.