Of all the arguments I’ve heard (on both sides of the issue), this one from Paul Graham seems to be the most level-headed and pragmatic:
Should people not be able to charge for content? There’s not a single yes or no answer to that question. People should be able to charge for content when it works to charge for content.
But by “works” I mean something more subtle than “when they can get away with it.” I mean when people can charge for content without warping society in order to do it. …
Ultimately it comes down to common sense. When you’re abusing the legal system by trying to use mass lawsuits against randomly chosen people as a form of exemplary punishment, or lobbying for laws that would break the Internet if they passed, that’s ipso facto evidence you’re using a definition of property that doesn’t work.