I've used air shocks extensively (almost exclusively), if you match the correct shock to your application, I've never experienced a problem. (numbers are a little arbitrary) Problem I see the most in a Full Body rig is that people see that a 2.0" 16" travel shock is $200 and can suuport 800 lbs and the 2.5" 16 travel shock for $500 can support 1800lbs. people tend to think that since the rear of a Jeep is about 1500 lbs, they can get away with running the 2.0 shock. problem is, you are basically working the shock at it's max potential 100% of the time, if start to go up an incline, you easily over come the shocks potential, they start to heat up and fatigue, the nitrogen charge inside becomes very dense and the shocks won't operate as they should. I will not install a 2.0 shock on any vehicle unless the entire vehicle weight is under 80% of the potential of 4 shocks. (so light weight comp buggy, zuki's, etc..) again the numbers above for weight and cost are just my round about guesses. we recently finished a 01 TJ with 2.5 kings all around, 14 in front, 16 in rear, on 42" irok stickies, the jeep sits a little over 3.75" over a stock TJ. about 2 inches of up travel and 10-12 of down travel. super stabile and very capabile. it was wheeled for 2 days straight and never has an issue with fatiguing.
What you may be refering to in the Original post is Air Bags used for over loading a pick up.
there was a company that made air bag suspension kits for tj's, really expensive and quite frankly, very useless.
EDIT: here is a vidoe from a couple weeks ago in the jeep I mentioned above, this was right after rebuilding the trans and was a test run in the snow
YouTube - My Movie