What on earth keeps the balloons apart and the line in tension? And what's the camera man in black hanging from, the top of one of the balloons? And what are the other balloons in the background doing, they all appear to be tethered?
The balloons are up against each other keeping the gap open, then the weight of the baskets and associated gear hanging below keeps everything vertical. Yes, the camera man is hanging from the top of the balloon, it's possible to sit on top of them - http://www.youtube.com/watch?v=toBnjmwsaRo
I wouldn't have thought the baskets were heavy enough to get the required line tension at what appears to be very modest dangle angles (or pitch/roll - meaningless terms for a balloon I guess). What do they weigh, 1500kg maybe and they can't be deflected more than 20deg from their at-rest alignment if that.
Huh... ~5kN line tension which is I guess just about enough.