As your Jeep piles on miles (especially difficult off-roading miles) components will wear and each make their own minor contribution to the problem. Add large, heavy tires on wheels that space them far out from the steering axis, and preventing death wobble can become quite a challenge. A steering stabilizer can help dampen the shimmy, but it's not a fix for the root cause(s) of the problem.
This is by no means a problem that's exclusive to Jeeps, but it's more commonly reported with them because so many more people modify theirs for extreme off-road use. I've had death wobble problems on most of my off-road vehicles over the years, and in my experience the number one cause of the problem has been welded steel wheels (which are rarely as concentric as a machined aluminum wheels) and out-of-round tires (Super Swampers are notoriously egg-shaped). However, the tires are only the start of the oscillation; the rest of the suspension and steering can either resist or compound the problem.
Rock Krawler Suspension put together a short video showing one of the common sources of the death wobble while they were diagnosing a customer's Jeep:
YouTube is full of videos showing 4x4 owners' fight against the dreaded death wobble. Here are two that illustrate the symptoms quite well:
I'm paying particular attention to the buildup of my Jeep to ensure that I will not have to deal with death wobble. I'm using nothing but the best steering, suspension, and ball joints, and my choice of wheels and tires is for ones that are as concentric as possible. My goal is to have steering that is smooth and free from death wobble even without a steering stabilizer installed. Stay tuned.
*** UPDATE 5/21/2013 ***
Diesel Power Magazine just published an article entitled Curing Death Wobble. They have listed and explained the 11 most frequent causes of steering shimmy:
- Tire Pressure
- Tire Balance
- Track Bar
- Tie Rod
- Drag Link
- Ball Joints
- Steering Damper
- Control Arm or Leaf Spring Bushings
- Wheel Bearings
- Steering Box