Almost right Here's a reasonable article that says since file sharing is so prevalent, but album sales are pretty much where they were, downloaded mp3s must be poor substitutes for CDs. This is a remarkably sensible observation, but leaves you wondering why.

I don't know the answer, but I'm guessing that demand for music is very elastic while demand for CDs is less so. This means I'm willing to listen to a song (for free) if someone suggests it, but I'm not going to buy a $15 CD just to check something out. But why would CD buyers continue to buy CDs when they can download everything for free online? Part of the answer is that CDs are more portable than mp3 players (iPod excepted, other portable mp3 players suck) and so are important for music on the go. A CD where every song is worth having is probably better value than the time spent finding and downloading them online. Or maybe people just like having CDs.