Wind turbines that operate well above the ground most emphatically ARE being built, and I'm surprised this fact hasn't more thoroughly penetrated the slashdot consciousness given how "sexy" this tech is. I have biases because I work in this field and have met most of the major players, but IMHO the two companies that are marching most rapidly towards utility scale aerial wind power are Makani power and Ampyx power:
http://www.makanipower.com/
http://www.ampyxpower.com/
In particular, Makani power's 30kW Wing 7b (same as wing 7a but with more aerodynamic turbine cowlings) is hitting their predicted power curve perfectly, and they're already working on their next wing. Ampyx is also using (way more efficient) rigid wings, but they do their power generation on the ground, which has a bunch of advantages and disadvantages. I'm not sure which design will ultimately be more efficient/practical (and this may depend on scale), but at the rate they're going it will certainly be hard to beat Makani to market. Also, for better or worse, national differences in the way airspace is regulated may play an accidental role in preventing the industry from rapidly standardizing on one design. Currently the FAA is (tentatively) regulating Makani's turbines as structures, and the govt. in the Netherlands is (tentatively) regulating Ampyx's turbines as aircraft. Note that there are a bunch of other start-ups working on AWE as well; the above two are just the ones I consider most promising for utility scale power.