By ecologically problematic, do you mean that if many passengers opt to fly with adjacent seats empty it would transitively mean that more flights would be needed to meet the demand? (if that is the case it absolutely makes sense !)
Doesn't the same argument apply to the existence of business class? Since to a very large extent, what you're paying for in business class is the extra square feet of cabin space.
This book Prosperity Without Growth [1] is a decent start from the perspective of an economist/environmentalist. It's somewhat hampered by the author's failure to rigorously define terms (a serious no-no for any economic/philosophical argument) but contains some good ideas.
Another great read from a more relate able angle is The Omnivore's Dilemma which doesn't address the issue very directly, but shows in painstaking detail how the US food chain has moved from a renewable solar base to one derived entirely from corn, which in turn relies on cheap petrochemical sources to grow at the speed, intensity, and volume that we grow it in the US.
Check out the reviews for both books as well - many of them cite other important works in the genre.
Hmm, I dunno... it relieves some of the financial pressure of having empty seats, by extracting some value from them. Therefore there will be less incentive for the airline to maximize seat utilization (through overbooking, for example, which saves money but costs reputation for the airline every time someone gets booted). Therefore we can expect seat utilization to go down.
That's true. That's a pretty complex effect, so you'd need some decent data to estimate its magnitude. But you're right it should be above zero, unless there's some other effect to suppress it.
I think they just make money from reshuffling empty seats they were gonna have anyway, not more than that. But I must admit I didn't read the article because my whole screen filled with junk while opening the website.