I've seen some points about them being a net negative on the environment, but I'm not qualified enough to say either way.
To provide a little perspective, here’s a link to a book I came across not long ago (written by a real-deal skater, no less) that goes into the above in some detail.
Def should buy if you are curious, or want to know more about wind energy.
In short, these things are “kicking the can down the road” to these 3rd world economies, where the gain from our new, decreased need for fossil fuel is offset or lost entirely by the strip mining, poisoning of rivers, deforestation, slavery, etc. that are required to produce these things in the first place.
Very interesting read. Recommended.