Just read this from an Inside Line review of a Long-Term S5:
There was another, more significant issue that arose. A pronounced vibration in the steering wheel at freeway speeds concerned us. The same symptom not-so-coincidentally developed in our long-term Audi A4 Avant. We worked with Audi of America and Santa Monica Audi to resolve the issue, which apparently had fielded similar complaints. With spin-balancing for the tires, about 90 percent of all issues were resolved, Audi told us. But we fell into the 10 percent that also required stiffer lower-front control arms to deliver the refinement we expected.
It makes you wonder if cost and weight considerations are driving carmakers to allowing a little more flex in the suspension components. It may be to help make the ride feel more compliant. Who knows? But event Audi has this problem. Interesting that it was a primary suspension component and not a bushing.