Magnatune founder (and CC board member) John Buckman in an opinion piece for Gig Magazine:

In 1980, Classical music represented 20% of global music sales. In 2000, Classical had plummeted to just 2% of global music sales. What happened? Did all those people suddenly lose their taste for classical music? Or is something else going on?

At Magnatune.com, an online record label I run, we sell six different genres of music, ranging from Ambient to Classical to Death Metal and World Music. Yet Classical represents a whopping 42% of our sales. Even more intriguingly, only 9% of the visitors to our music site click on “classical” as the genre they’re interested in, yet almost half of them end up buying classical music. What’s going on here?

CC licensing is part of the answer, but go read the article for a number of other keen observations.