Ars Technica - There is a perennial debate in tech policy circles about whether peer-to-peer file sharing reduces the market for music and other creative content. It's obvious why those who download pirated files from peer-to-peer networks might purchase less content through legitimate channels. But some scholars argue file sharing can make it easier for fans to find new content they like, broadening their tastes and causing them to buy more music in the long run.
[A Columbia University] survey provides some limited support for the view that file
sharing promotes, rather than hinders, legitimate music purchases. The
average American on a peer-to-peer network has a music library
of almost 2000 songs. Of these, 760 (38 percent) are reported to be
legitimately purchased. In contrast, those who say they are not P2P
users (but do collect digital music files) have an average library size
of 1300 songs. Of those, 582 (roughly 45 percent) were purchased from
legitimate sources. Most of the others were ripped from CDs or copied
from friends and family.