Amie.st : a website for legal song downloads that did demand-based pricing. Prices started at zero but as they became more popular, their value would rise. You

Amie.st : a website for legal song downloads that did demand-based pricing. Prices started at zero but as they became more popular, their value would rise. You could also "recommend" songs and if their value rose, you'd get the difference in value credited to you. Rewarded early participants in music discovery. Clever mechanic.