Perhaps you could look at the story behind BearShare (wiki link.) The music biz attempted a commercialized protocol of their own, trying to capture the popularity of the original BearShare that ran on the gnutella network. But their network closed down earlier this year. This suggests it was not especially successful.

There is nothing whatsoever illegal about the Gnutella protocol. Are cars illegal or is it the drivers that make mistakes (deliberately or accidentally.)

Many people have absolutely no idea the interest some people have in the non-copyright material people seek on the gnutella network. But once the reputation was stained, branded and letter-boxed, the total misconception is that the gnutella network is for non-legal activities.