One thing the article doesn't mention is that, by the very nature of a tethered, floating wind turbine, dozens could be floated up on the same tether, providing orders of magnitude more power at a smaller ground footprint than even small wind turbines.
This could easily start a revolution in localized power generation. By nature of the technology, we can't place these much closer together than the added lengths of their tethers, but again, the ability to tether multiple ones together high up into the sky negates that disadvantage several times, and naturally means that the ground tether point could fit into the space of an average backyard. Entire communities could be powered just from a few "stacks" of these airborne generators. Also, because of the high visibility of the generators themselves, they're unlikely to cause problems with migrant bird populations. But, if problems do arise, it wouldn't be too difficult to put a more visible mesh in front of the prop.
These can even be placed out in the ocean with fewer consequences and lower cost than those ocean-based turbines.

that doesn't look like it'd be very efficient. I think something like this http://en.wikipedia.org/wiki/Airborne_wind_turbine would be much better.
And in either case... with the development of thin/flexible/spray-on "solar cells" when they become fully/commercially available you could coat the outter shell of these with that, so that they are producing wind/solar power at the same time from one unit.

Man, there are a lot of trendy, science-ignorant hippie investors out there continuing to burn their money on this fluff. It is probably a great way to impress hippie chicks though.
Guys, alt-counterculture was cool in poetry and music in the sixties. But you can't do it with power generation. It has to actually generate power.

Helium? Why?
The people in Germany made perfectly good vehicles that used hydrogen.
They were safe and impervious to combustion - except when the captain did a turn that exceeded the hulls designed stress limits, broke a truss wire that slices open a gas cell, and the leak was ignited by static.
I think nice land based solar concentrators are the go....

I wonder how much of the electricity produced would be required to provide enough hydrogen to keep the "balloon" inflated.

Oh dear! So Helium is free these days, or what? Helium is rare and it is getting rarer by the minute. We need it for supercooling MRIs and other life saving devices. We can not afford loosing it to thousands of blimps for turbines (which are loosing helium at an alarming rate). So I really dont think that this is a good idea. If they used hydrogen, maybe... It is yet another "high flying" green idea that I doubt will ever "take off" ;)

If these can get twice the effect of land based ones then there are other technical advances that can help.
doesn't a version of ultra thin graphene stop helium 100%?? This is perfect for that.
One guy designed a turbine shroud based on the whale sharks mouth that seriously reduced drag and improved generator speeds. If these can be placed out to sea in turbine fields or over farmers fields so they generate an income for the farmer then this is a better idea.
One negative is that the increased fan speed and height will kill a lot more birds unless the tethered height is quite high. Landbased windmills have relative slow speeds turbines are smaller but operate much faster.
As for using hydrogen.. hydrogen explodes and the balloon falls to earth in a fireball. Helium leaks out and then the balloon falls to earth slowly.
Helium doesn't get used up its recyclable. It's the tech using liquid helium to cool superconductors that is 'using' up all the helium. I'm OK with CERN doing that but the people trying to make fusion work are wasting their time. Of course if they do get it running there's your new source of helium..

BTW: The USA has the only Helium well in the World in Texas...
Solar (of all flavors) is now on the move and I expect that the traditional Energy Companies and especially the Nuclear Industry will fight tooth and nail to "keep Solar in it's place" a tiny fraction of the total...
Solar (of all flavors ) is ready for prime time, unless the Nuclear Fascists* stop it from happening!
Benefits of Solar (of all flavors): ✔ Less costly to build ✔ ZERO RISK OF A MELTDOWN ✔ No Trillion Dollar Eco-Disasters ✔ Faster to construct ✔ CLEAN from start to finsh. ✔ No radiation worries or leaks ✔ No foreign dependency ✔ Prices dropping yearly ✔ Creates green jobs ✔ No nuclear cleanup expenses
Read one or more of these, to learn how Solar (especially Solar from Space) can power the Planet and put a stop to Warfare over energy and minerals:
The High Frontier by Gerard K. O'Neill, Colonies In Space by A. Heppenheim­er. The Third Industrial Revolution G. Harry Stine The Space Enterprise by Philip Robert Harris

If razing mountaintops for noisy unsightly wind turbines is a good idea, then this is a much better idea. I like how it can be portable and deployed where needed. Helium is found in natural gas, mostly in the USA. It can also be a byproduct of Thorium fission reactors LFTR MSR, which we are shamefully late to develop and deploy. Solutions to our energy problems must be taken as a spectrum that reenforce each other. Hydrogen would be a very bad choice for this -- it is hard to contain, and it goes boom. Helium could also be recycled. It is primarily keeping it from leaking that is important for this aspect.

@ Karsten Evans
Birds.... come on, lets get real, that is hardly a problem. Birds aren't going to just go flying into a realatively stationairy object. Its not a like a plane that is fast moving, always in a different location.
Hydrogen doesn't just explode on its own, it has to have a cause. And that is hardly a problem we need to worry about. It would most likely be rare in the first place which is good (financially) but we're not talking about a blimp, there would be no people to get injured. If such a device exploded/lit on fire, it would be out by the time it hit the ground.
Helium can be recycleable in certain conditions, but you can't capture it from the atmosphere (because its too expensive) and yes helium does run out. It is deffinately one of the more limited resources available on this planet, and the supply is only further running out.