Copyright law is not limited to a particular medium, but is intended to protect IP (intellectual property) and is therefore equally relevant to all media.Originally Posted by Natobasso
Natobasso has made a very important point... MONEY! However, there is a wider debate, and although the law is used to protect IP and by extension preserve income, its focus is not (soley) financial. Laws are created to protect rights, so it's worth remembering that (financial) gain is not only measured in direct remuneration (ie. burn a disk of somebody else's stuff, and sell it), but also in longer term benefits, such as exposure and subsequent fame.
Stealing the IP of another individual is against the law, even without financial gain. If you distribute work passed off as your own, which was actually created by another individual, you are in effect claiming that that individual is not the author, but in fact you are. This is fairly clear infringement of copyright, and is exactly the sort of thing that ends up in court.