This article in the Times Online (UK) presents an interesting discussion on the Long Tail theory. The article claims that the sheer amount of unsold songs available online, shows that the promise of the Long Tail is not being realized.

Upon a closer look at the data, and a scan of the comments, it is clear that in terms of percentages (which is fairly course grained) that the tail based on the available data is not particularly long in comparison to the total amount available material. True. However, the sheer number (we're talking 10s of 1000s) of additional albums, EPs and singles being sold, that otherwise wouldn't be even stocked in your HMV, Virgin or Sam Goody's points to the Long Tail theory is action!

Additionally as has already been pointed out, its perhaps a bit early to be drawing long term or final conclusions as the marketplace is barely nascent!

Full Article @ the timesonline.co.uk