Readers usually ask this question about mosquitoes! I reply that complete eradication of these flying disease vectors would be a boon to mankind. More than 200 million people were infected with malaria last year; mosquitoes also spread encephalitis, yellow fever, meningitis, dengue fever, and more. But then I hear from people who worry about the food chain. They say that if it weren’t for mosquitoes, certain other animals—those who feed on them—may die off, and so on. These people believe that every organism fills a crucial niche and that the balance of nature is delicate. Bedbugs provide some evidence this is not true. After World War II, insecticides such as DDT virtually eliminated these pests in this country, Canada, and Europe. Bedbugs were gone for decades and didn’t reappear until almost the new millennium. Did anything bad happen to the food chain in these parts of the world? No. The food chain isn’t static. Living things evolve and disappear; environments are transformed. In short, nature is all about change.
One thing that vos Savant neglects to mention is that the extinction of mosquitoes isn't going to happen on its own. While non-freaks may not like to think about mosquito sex, the fact is that these critters aren't spontaneously going to lose their drive to procreate. So eliminating them - as opposed to the necessary control of their populations - would involve a staggering amount of pesticide. And yes, that would adversely affect birds, small mammals, and ultimately people
Also if nature abhors a vacuum it's not too crazy to imagine another species stepping into the role of human blood feeder/occasional disease vector. But I assume that will remain a moot point.