"All "good people" should want the eradication of mosquitos, but we don't know how that will ultimately affect the balance of the ecosystem."

Indeed... this is where the Law of Unintended Consequences often bites us. It reminds me of the old story of how the French tried to eradicate the rat problem in Hanoi by paying for dead rats. The people began to farm rats to maximize their payments, increasing the rat population, not decreasing it.

The bad thing about unintended consequences and perverse incentives is that we cannot always predict where they will appear. So many times have we (as a species) tried to combat something by introducing a foreign species of some other animal, only to find that now we have a new problem, which may be worse than the one that was supposed to be (and usually wasn't) solved.