I'm as big a fan of wind power as anyone around; I started Renewable Choice Energy in 2001 (now one of the nations leading provider of wind credits) and I think wind power needs to be a big part of the solution to the world's problem of dirty energy.
But small wind turbines have never struck me as something to get excited about. Industrial turbines are huge machines, towering more than four hundred feet with massive 250' foot blades churning through the air. Small turbines have blades that are 3-15 feet across and they rarely sit over 100 feet up in the air.
Zeeland, a Dutch province, ran a year long test with twelve different small turbines setup across a windy field. The results were pretty dismal- three of the turbines broke, the others generated just trickles of energy. The smaller the turbine, the sharper the dropoff in energy production was. The three foot wide Energy Ball would be hard pressed to reliably keep a CFL bulb lit.
Their performance is further sullied when you consider the lower windspeeds most urban and residential settings have. Trees and buildings are windspeed killers and are both abundant where small turbines are most likely to be placed.
A good illustration of wind's economy of scale is the energy generated by a 60 foot wide industrial turbine near the test site- though it only cost 17% more than all twelve small turbines combined, it created over 20 more energy.
Low-tech Magazine said it best on this one
Wind power rules, but small windmills are a swindle. Bigger is, in this case, better.