I brought this up a bit in class today: "Good Copy, Bad Copy" has led me to think about creative boundaries. I gathered from the documentary that new artists like Girl Talk and Danger Mouse, when sampling different songs, consider these boundaries to be less substantial than in the past, while legal representatives would likely disagree.
I think one of the main points, if not the main point, in the debate is whether or not it is creative to use someone else's established work in a new endeavor. Girl Talk refers to himself as a DJ, not a songwriter, making the distinction that he isn't trying to claim a musician's songs as his own composition. Yet his mash-ups consist of multiple songs to make entirely new songs.
In the text realm, we know this sampling takes place every day in academic papers. Quoting other authors of all kind of writing is a fact of life. That there is little to no uproar about this may stem from the fact that academic writing is not popularly considered to be "art." Sources are clearly cited, names are given, and no one calls out an essayist on copyright infringement.
The "art" world, however, is a different story. It's rare that a bestselling fiction author doesn't at some point get slammed with a lawsuit claiming s/he plagiarized an earlier, less commercially successful book. I would venture a guess that, aside from lamenting potential money lost, these plaintiff's are offended by the possibility that someone might do better with a similar idea or piece of work that they themselves had or created, that another writer's creativity can overpower their own. Academic writing isn't threatening in this regard.
On a related note, author's tend to take up differing opinions about how "free" their work ought to be. J.K. Rowling, for example, is not offended by and in fact encourages young people to use her characters and their world to write their own stories, believing that any creation is creative. Stephen King takes the opposite view, as I've read, and denounces the recycling of his stories.
It cannot be denied that this "copying" is becoming ubiquitous. Go to any Barnes & Noble, and you'll find a plethora of titles that have turned Mr. Darcy into a vampire or Jane Eyre into a modern-day college student who falls in love with a rock star. (No, I did not make these up.)