There's a discussion on the Awful Forums about whether Apple's iPod will be dethroned as the king of portable music players anytime soon. One of the main points was that the iPod does not support Ogg Vorbis playback, while many of its competitors do.
For those of you who have managed to avoid hearing about Ogg Vorbis, it's an open-source audio compression format, very similar to MP3, with no licensing restrictions. It has a few other minor benefits, such as slightly better quality at lower bitrates. The biggest limitation of the MP3 format is that the length of a file can only be a multiple of a certain time interval, so MP3s usually have a small split-second silence at the end. This is why it's difficult to play MP3s of tracks that blend into each other without having a small gap between them. Ogg Vorbis supports "gapless playback," meaning that the files can be of any precise duration and tracks can be played continuously.
The problem is that there really aren't any other advantages to Ogg. This is why it will never matter in the general marketplace. Just like DVD-Audio and the SACD The quality difference is minimal, and hardly anyone cares that Ogg is completely "free" because MP3 is close enough and its restrictions don't interfere with most users.
Switching to Ogg is not an improvement. It's a giant step sideways. Consequently, hardly anyone uses it. Why would Apple bother to support something when there's no demand?