Wind energy…the way of the future or a menace ?

I am wondering…since here we see that 70% efficiency can be reached…why we still cling on to the propellers as a wind energy systems ?[ATTACH=JSON]{“alt”:”Click image for larger version Name:tvertical-axis-wind-turbine.jpg Views:t0 Size:t85.2 KB ID:t3862358″,”data-align”:”none”,”data-attachmentid”:”3862358″,”data-size”:”full”}[/ATTACH]