I have and I'm sure the mosquito nets are effective.
The point isn't to say they're not, but rather to say the nations that have been most successful at preventing malaria deaths are those that are most developed, or have access to anti-malarial drugs (which are dirt cheap).
The flu kills thousands every year and used to kill many more (the 1918 flu epidemic killed an estimated 50 to 100 million people around the world), but we don't even consider it to be fatal anymore due to our level of nutrition and medical care - which comes from development.
Also keep in mind the US used to have malaria-spreading mosquitoes and a fair amount of malaria-deaths, but now it's considered eliminated as a public health concern. Maybe some of the techniques it used could be applied to Africa, and not just band-aids that keep Africa hooked on western 'aid'.