I'm not an expert, but I've been doing a little research on audio file compression to cut down on Amazon S3 charges for a personal site I have up that suddenly got a fair amount of traffic. The way I understand it, ogg vorbis files actually compress better than mp3s, so they're better on a quality/size ratio. A 3MB ogg file will generally sound better than a 3MB mp3 file.

I think the reason Amazon might not be supporting them is that not all browsers can play them natively — specifically, Safari needs a plug-in to play them. So, for my site, which is using jPlayer, I have to compress all the files as .oga and .mp3, then set up the mp3s as a fallback so Safari will stream them.

Almost no one uses Ogg, not a very glaring omission in my opinion. Amazon sells MP3s. Apple sells AACs. No one with any market share sells Ogg files.

This doesn't apply here but it is interesting: there is one major player making heavy use of ogg, and that is spotify. All their streaming is done in ogg.

AFAIK all games sound and music have been in ogg format for ages.

And none of that would be in Amazon Music... Again, no one with any serious market share sells music in Ogg.

The amount of music sold in file format is totally dwarved by the amount sold on CDs. For a while I used to rip to ogg, I'm probably not the only one.

My assumption is that this is a strategic move against Apple and ipod/iphone doesn't support ogg, so it doesn't come into play. Just a guess.