I suppose people don't really know how the volume limit functions. It's designed in the way that there is no volume higher than 100dB going out of the device, so it doesn't work the same way for each album.
Some albums, like pop albums, are mastered very loudly, so if you limit a devices volume to make the pop/rock albums stay under 100dB at all times,
when you listen to a classical album, which has more dynamic range, it'll be mastered at a much lower volume, to make it possible that there's no distortion when the dynamic range changes.
So a device set on maximal volume will give you maybe 70dB on a classical albums most parts, with 90-93dB on the loudest parts, sometimes even less.
So it'll be basically barely audible if you are in a loud environment.
If the devices worked "smart", i.e. did the volume adjustment according to the music it is playing, then 100dB would indeed be an OK upper bound.
But they don't.
On my US iPod nano, I set the volume to 40% when listening to pop, and I can hear it easily on the road, but when I listen to classical, the volume is at 80-85% mostly, to get the same loudness.
I hope it's clear for everyone now and why it's totally nonsense to set a limit like that on EU iPods, which makes everyone furious.