I think it is incorrect to assume that if channels for downloading music 'illegally' without paying were removed that those who indulged in such practices would go to the store and buy the same music.
So yes there is a legal argument to be made that downloading/filesharing is 'stealing'. However it's quite another thing to suppose that such activities are destroying music sales to the extent that some might have us believe.
The success of online music retail (eg iTunes) would strongly suggest that there is a new type of market opening up. Different medium, different distribution channels, different market factors, different politics, an quite possibly a different (read: larger) customer/fan base.
While I may have reservations over the quality of the product (the ubiquitous 128kbps MP3!) I also can't wait to see what happens next!