Here's a piece from WIRED about the prospects for large-scale use of wind power generated at high altitudes. It's not a bad article, full of gee-whiz and enthusiasm for the idea. It even notes, optimistically, that high-altitude wind power can be tapped directly over major population centers, instead of having to put wind farms on the ground out in the middle of nowhere.
Interestingly, there's a word missing from the article. The word is "airplane." Areas of high population density are also areas with lots of air traffic. Putting what amounts to barrage balloons, reaching up to 40,000 feet, right in the middle of busy air corridors seems to be somewhere between "really stupid" and "incredibly dangerous."
If only we could tap the mighty power of the Atom . . .