It probably goes without saying,
It probably goes without saying, but I think filepile (the new beta site that should launch any day now) could be bigger than napster. Where else can you easily find, discuss, and download Mojo Nixon's 'are you drinking with me, jesus?'
Since the trading part is kind of a pain (you have to wait a while when you upload something), I doubt it ever becomes a way to traffic entire albums. But you get a taste of something good, something offbeat, and it makes you want more. I hope the quality stays up when it gets more exposure, or someone like CDnow wakes up and realizes it's a cool way to preview tracks.
The best part of the site is that it's a very simple and cool idea that andre came up with. It doesn't use any new technology and could have been made three years ago. The concepts have been sitting under our noses this whole time and it only required one smart person to do a week or two of programming and a great site was born.
Those are the best kind of ideas, the ones that combine simple concepts in a new and elegant way, producing breakthrough sites.