You're all a little wrong. The fact is that it is possible to have normal wear on components and have each individual piece not by itself in need of immediate replacement but the combined vibrations hit resonance with each other, causing a major change in the severity of vibration, measured in amplitude.
When a trombone hits resonance you hear one note much louder than all the others, thus creating music. All the other frequencies are always present but only one, as determined by length of tube, will attenuate and resonate louder than all the others combined. The graph shows a huge spike that multiplies the intensity many times greater than what it would be otherwise. Lots of little things sometimes work together and create one big thing.
http://en.wikipedia.org/wiki/ResonanceThe front of an Eagle has a rotating mechanism, the engine, bolted to a different rotating mechanism, the transmission, also bolted to a third mechanism, the front axle. They are unusually susceptible to resonance and I've seen some crazy amount of harmonic motion from mine that immediately went away as soon as the steering dampner was replaced.
By all means it could be an unsafe condition ready to break and kill you, so act accordingly and start replacing stuff and giving your steering very close scrutiny.
If he was to replace all of his components with new stuff it might go away just because resonance can't happen if you take away the contributing vibrations. Ideally nothing should be vibrating. Ideally your tires are balanced, your alignment freshly checked, and so forth. You should be able to disconnect the steering stabilizer and see no change anywhere. It could be hiding a Pitman arm or other major component about to fail and it could be a dangerous band aid to ignore.
It is possible, however, that you won't find anything majorly wrong and replacing stuff doesn't make it go away except for the steering stabilizer. It is possible that lack of steering stabilizer will cause vibrations to resonate with each, thus causing damage to components. The plates in my battery actually broke free from how violent the perfectly periodic motion my Eagle sedan had. It's possible that ignoring the condition of your steering stabilizer will speed up the aging process and force you to replace parts earlier than you would have otherwise had to.
I have two ABET accredited BE degrees that spent a considerable amount of time discussing harmonic motion in cars and the differential calculations of periodic motion in both mechanical systems and electrical systems. We specifically studied Ralph Nader's argument that poor damping rates on the shocks caused the death of a young man who drove a steady speed across evenly spaced road bumps, thus causing a resonant standing wave and loss of control in a vehicle in otherwise factory original condition. It's possible.