These sites are important to the success of acts. Retailers burn CDs on demand. A successful act is one with a small, loyal following. The market depolarizes. Instead of a few acts making huge sums of money, there are many acts making modest sums.
Mass culture demands super stars.
There will always be a few acts with millions of fans. Record labels count success in dollars. Musical acts today count success in gold records. They maintain monopoly prices on the consumer side by, for example, conspiring to fix prices . Courtney Love has a lucid and detailed account of how they work the game on the producer side.