From what I´ve read the limit is 100dB and thats reasonable but a 100dB from in-ear will not be 100dB from large openair headphones. My big headphone was almost useless with the iPod and not all of use use in-ear all the time.
I´ve read on some iPod forums that the volume limit i EU is due to some regulation in France not permitting to loud volume. All my former iPods had the limit even though they were bought in Sweden. Maybe Sony has adapted the limit to the countries that apply the limits.
Confirm this working om my NWZ-A818. However mine has volume limit set to off, and is uncapped despite the fact that I bought it within the EU. I bought it in Sweden som maybe not all EU countries have this limit enabled.