Aaron Swartz proposes a crypto based compulsory licensing scheme:

So when you buy a CD or DVD burner, it comes with a short string (a random-looking series of letters and numbers) to type into your computer. (The strings are given to the manufacturers by the government when they pay the tax.) When you pay the bill for your Internet connection, you’re emailed another such string. (The string from your email can be handled automatically, and the one in the CD burner box could be made relatively easy to type in.)

The string is a digital gift certificate, worth however much the tax you paid was, but only spendable on donations to artists. Once your computer has the string, it looks at all the songs you’ve listened to and decides what songs to spend your gift certificate money on. (It knows what you listen to because it’s built in to your MP3 player.) If you’ve listened to one Britney Spears song day and night for the past month and nothing else, it will give all your money to Britney. If you listen to a variety of independent bands, it will split your money among them. (Advanced users can of course customize how their money will be spent, but it’s simpler to have the computer choose automatically by default.)