Completely aside from the issue of file sharing is the artistic use of other people's copyrighted information in one's own work. And I do think that the legal penalties of this have to be looked at in a case-by-case basis... Is the perpetrator a non-professional individual who sampled someone who is represented by a major label, or is the perpetrator a professional musician on a major label who has sampled someone with no representation at all? The discrepancy between the individual defendant with almost no money for lawyers and the major label with almost unlimited money for a lawsuit is where copyright law seems to break down in my opinion. Obviously, if copyright law is a completely even playing field, then it is much easier for the people represented by major companies to defend the appropriation of songs or images than it is for individuals to defend the appropriation of songs or images from major companies.
First, look at a relatively unknown 1980's techno band called Cybotron. Listen to the keyboard track that starts at the 00:30" second mark and then compare it to the next video.
Now, compare that to the award winning Missy Elliot song and you will quickly realize that it is the exact same song with different lyrics and some re-engineering. To my knowledge there has been no evidence of a lawsuit.
And then compare that to a relatively unknown experimental band called Negativeland, who did an ironic spoof of a song by a more famous band called U2 as well as a radio announcer named Kasey Kasem.... I think you can guess what kind of lawsuit they got slapped with.