Geez, I read a similar article earlier today but didn't make a connection to astronomy ...
All we need, more high flying junk. They will be trying to block the suns harmfull rays soon with a blanket of balloons.
I really don't see how a balloon 20km up is going to affect our night skies. It will be in the Earth's shadow before twilight even ends and thus be invisible. If anything, existing satellites and aircraft have more of an "impact" on the night sky....
More clutter above, as if satellites weren't enough... These darn things will have solar panels and be just big enough to be seen telescopically, if you are lookig at the right place at the right time. But they'll show up in fairly deep images, producing trails across your image.
The idea is novel. Its effect on astronomy will be negligable. It is all about putting transponders into low orbits to give internet coverage, and much cheaper than launching satellites.
At 60,000 feet and moving at high speed (air currents) they may appear as streaks on some photograpic exposures but this would only be spasmodic. To have one pass through your specific 1 degree FOV would be quite rare.
If you look at the practicality of such as scheme it starts to look a bit ambitious. At 60,000 ft the coverage would be at least 200 km. Still requiring hundreds of balloons to give good coverage. You would need a special transponder on the ground (I bet Google would know how to charge for that)
The transponder and power unit could be mass produced quite cheaply. Even a suitable ballon would not be prohibitively expensive. The balloon would be charged with hydrogen to a level that would give neutral boyancy at 60,000 feet.
However the hydrogen molecules would slowly migrate through the fabric of the balloon requiring a supply of hydrogen to re-charge the system to keep it in orbit and in any case eventually the ballon will return slowly to earth (unless it bursts due to many causes), what fun!. (Wear your hard hats at all times)
Barry
PS I don't think it will ever happen past the experimental stage.
I found this article a little disturbing, as it may affect our night skies:
This is independence day kind of stuff. 
