Compulsory Licensing.
Record labels: how much would I have to pay you to be allowed to sell an MP3 of one of your songs to someone else? Can you refuse to license the copying?
Incentive.
How many people do you think would share their files for free if there was a system that allowed them to charge the person at the other end a small fee?
Decentralised distribution.
Soulseek with 2 extra columns: Price and Reputation.
Reputation.
Pioneered by EBay: caveat vendor.
Affordable.
Fixed price per track (see compulsory licensing), plus a variable vendor-added percentage.
1000 words:
A trader lists their files on the network, and sets a percentage commission for each file based on perceived value. A buyer searches the network, or links in from an external recommendation, or browses a trader's files. The buyer receives prices (fixed price + percentage added), full track info and the vendor's reputation details, plus a direct connection for instant messaging. The buyer then requests the download from their chosen vendor.
When the vendor's machine reaches 25% of the upload, it requests payment from the central payment control server. The payment control server requests authorisation from the buyer, who can listen to the already downloaded preview. Once the central server receives authorisation from the buyer, the transaction occurs and the download continues.
Feedback.
If the download is broken or slow, or the sound quality is bad, or the file is not as advertised, the buyer provides a bad rating for the vendor. If the service was good, they provide a good rating, and this information is stored in the central reputation server.
Erosion.
The system runs alongside the current, free system. If vendors don't want to charge, or want to offer free samples, that's fine. As tracks become available for licensing they will be marked in the vendor's library, allowing the vendor to select the price they would like to charge for each file.