During the straight ski days typical waist lengths averaged about 62-64mm, sometimes 65mm. I don't think it was the waist width per se that held beginners back. If anything, following the ice skate analogy, the closer the edge is to the foot the better control and response a person should have.
Since even some of super narrow 60mm waisted skis of the past still offer a platform much wider than an ice skate blade, I don't think balance was ever that much of an issue. Other than that observation, I agree with everything else that has been said on the subject, so far. I do find it amusing that the 60mm "waip waisted" ski of not long ago is now being called "wasp waisted" at 68-70mm. Everything is relative, I guess.
I would add one other possible factor into the mix: carvers tend to evolve as detuned, race skis. FIS standards for length and radius (though scheduled to change in the 2008 season) have remained unchanged for several seasons now. That has somewhat limited what the manufacturers can do other than just tweaking their race models and the "skier-cross" and "carving" ski development has also perhaps been somewhat stifled, as a result. Even the "short slaloms" that were the "do it all" skis of the west of just a few seasons ago owed a lot to race SL race skis in terms of both length and torsional stiffness.
I have visions of all these folks skiing the green and blue groomers with their new 85-100+mm waisted skis this upcoming season. However, if it puts more people on skis so much the better, I guess. If it encourages more people to venture off the groomed so much the better, as well. what does concern me is you may see more unqualified skiers venturing out of bounds or into the back country who aren't qualified to do so.. That seems to be a growing problem even now with some very tragic outcomes.
At the end of the day though, if most skiers still demand groomed runs than I suspect that we will see an evolution back toward narrower waisted carving type skis as the tool of choice. With the scheduled FIS changes in 2008, I suspect we will also see a trend back to somewhat longer GS type recreational skis, as well.