Tim O'Reilly and Nick Carr debate this idea on O'Reilly Radar. Carr agrees that piracy can indeed bring to an artist the benefits of exposure, but adds a crucial point:

I think it's critical to point out that piracy is only good so long as it's bad. In other words, there have to be real costs (social, legal, technological) to taking the pirate route in order to prevent it from displacing too many sales. As soon as piracy becomes legitimate, the balance tips way over to the bad side. By lending legitimacy to piracy, O'Reilly may, unintentionally, end up promoting the ill effects of piracy and hence weakening his own argument.

Those with a taste for drollery will be amused by O'Reilly's defense of piracy, considering that a couple of months ago he got into a hard-edged dispute with his community after he propertized the term "Web 2.0" by registering it as a service mark for conferences.