Bandcamp has a great post on their blog showing the results of inbound website traffic data. At least for Bandcamp, it shows that some users of freeloader websites still end up buying music, with a number of great examples.
It ends with some inspiring hope from the innovative company:
When we first launched Bandcamp, the conventional wisdom was that music retail was moribund, and that artists’ futures were all about those terrifically lucrative tours you guys go on, supplemented perhaps by trickle-down advertising revenue generated by millions of listeners enjoying your tunes while doing their best to ignore ads for toothpaste. Fortunately, it appears there’s still a thriving community of fans who understand that the best way to support the artists they love is by handing them money.