Anyone who thinks freeloading isn't a problem on the network should read this study. Admittedly it is 2 years old, but I'd bet money it still applies. It certainly reflects my experience on Napster just a year ago. It concludes:

"Specifically, we found that nearly 70% of Gnutella users share no files, and nearly 50% of all responses are returned by the top 1% of sharing hosts"

http://www.firstmonday.dk/issues/issue5_10/adar/