I wouln't be surprised if Microsoft Vista doesn't disable MP3s in the future, just as it has disabled other functions, such as S/PDIF optical interface.
http://www.cs.auckland.ac.nz/~pgut001/pubs/vista_cost.html
The next Vista update probably *will* disable them.
This kind of spells doom for the Zune, too....
I suspect Apple is probably safe, since they're using Lucent components in the iPod, if I recall correctly.