Here in the western U.S., where the towers are erected by the hundreds at a time, they've produced a number of drawbacks that weren't expected. Firstly, the environmenatalists are upset since they kill birds by the dozens, including migrating ducks and geese in the Central Flyway.
Secondly, the are very noisy, especially when hundreds of them are operating at one time...
Additionally, here, where electricity from coal fired plants is extremely cheap to produce, the wind towers cannot compete. "Critically important among the elements of true cost that are often understated or ignored by wind energy advocates is the huge cost of tax breaks and subsidies provided to the wind industry. Initially, tax breaks and subsidies for wind energy were justified on grounds that they were necessary to help an emerging technology compete with existing technologies for producing electricity until the technology was more thoroughly developed and demonstrated.
Federal, state and local government tax breaks and subsidies for wind energy have become so prevalent that it’s virtually certain that the politicians and regulators who provide them have no understanding of their magnitude and cost. It’s also virtually certain that they have not weighed benefits and costs. If they really have done either, there is no question but that they have decided to put the special interest of the wind industry ahead of the interests of taxpayers and electric customers who are paying for their largess." (Source: National wind watch.org)