A couple of things:
The point that people are getting taller is bang on the money. The 'standard' UK bed increased in length, at some point between the 1960s and the 1990s, from 6 ft. 0 ins to 6 ft. 6 ins. I don't need to remind you of what happened to airline seat pitch during this period...
Channel 4 News reported this evening that seat pitch on this partcular JMC flight to Calgary had been 28 inches. I am 6'3" and have suffered 2.5 hour charter flights to and from the Med in similar seats. I wouldn't dream of attempting it long haul.
The comfort thing is a real issue. After Virgin reduced its economy class seat pitch from 34 to 31 inches I made a vow never to fly economy long-haul again. What this means is that I spend more time in Europe, use airmiles to upgrade to business when I travel longhaul, or, when I really have to, take the pain and shell out for business. Yes, I paid BA over £5,000 to take my girlfriend and I to BGI over New Year (should keep you Nigels in business for an extra 3 minutes or so!). Lucky me - I can afford to do that occasionally - most tall people cannot.
Essentially, I view the economy seat pitch as unfair to taller people. It's not my fault I'm tall - and I'm hardly a monster. Small people get to pay a few hundred quid to travel and can be reasonably comfortable; I need repeat visits to the chiropractor if I try the same trick. In essence, I am being blackmailed to travel further up the plane.
As for the economics, it can't be that disastrous if AA can run with a sensible (read: pre-1994) transatlantic seat. It's up to regulators to regulate the market to stop the inevitable squeezing of pitch downwards, and I hope they come up with a sensible number - and by that, I mean over 31 inches.