So you're absolutely convinced that a Napster-like service is going to be used overwhelmingly for legal purposes? Uh-huh.
If he lives in the US, he doesn't have to be. He only has to - by virtue of Sony Corp v. Universal City Studios, Inc. (464 US 417 / 1984) - prove that there EXISTS a legal use for it.
If he lives outside the US, he is free to ignore US copyright at his leisure.
The courts have come down against Napster, even if the word isn't final yet.
Any court which DOES come down on Napster obviously hasn't read the very clear decision by the Supreme Court of the United States, and it will obviously go that far, if need be, so that they can reaffirm that which they have already stated.
D