I've always wondered what the long term impact of letting people pay 99 cents for the songs they want (instead of buying a CD containing 2 songs they want and 10 they don't for $17.99) would do to the recording industry. Time will tell, I suppose.
Based on comments Weird Al Yankovic recently made, The Digital Music Weblog set out to compute the difference between what an artist receives per song on a CD vs a downloaded albumn. The results...31 cents per song via CD, and 4.5 cents per song downloaded. OUCH. Do read the DMW post...very interesting discussion of how recording artists are compensated.
Yet another reason not to buy proprietary digital downloads.