Radiohead has made an interesting move by releasing its new album on a pay-what-you-will basis. In an article I started drafting in 2000, I suggested that musicians can succeed under this model so long as purchasers think of the transaction as a show of support. Whether characterized as the "warm glow" of do-gooder consumption or as a refletion of the restitutionary impulse that Wendy Gordon argues is at the base of copyright law, it is not surprising that people are paying for something they can download for free.
The risk in this model is that the frame of the transaction depends on perceptions and norms. If the frame switches to that of neoclassical economics, in which consumers and producers are adverse parties competing for a larger share of surplus, then the model fails. Stephen King seemed to think his experiment along these lines was a failure, and if it was, it may be because he charged a specific price ($1) for each installment of his serialized novel.