Most of Europe, at least. I'm in Lithuania and it is not available. On the other hand, not even Apple bothers to open the iTunes store here, despite successfully selling localized iPhones. And they wonder why piracy is so rampant here..
Anyway, I was actually thinking about buying a subscription with Last.fm. Since they don't put a 30 second limit on tracks in playlists I create as a subscriber, I could probably go listening through their whole library. This seems to be close to an 'all you can eat' model - at least for the tracks that have the preview/play icon next to them. Their music library seems decent, and I think the streaming works over HTTP, so it may be even possible to wget some of the tracks.