Robert Cookson's @robert_cookson article in the FT is fascinating - it seems Chris Anderson's Long Tail is not happening for music online.

One reason suggested is that digital music services have to sell in a limited amount of real estate so the big revenue drivers get featured to the detriment of smaller players.

Another possible reason is Globalisation - it is now easier to sell a British act into, say, New Zealand through online outlets such as iTunes than previously. Thus international Superstars are muscling out acts that would previously have been in the local 1%.