In this short video, explainmaestro C.G.P Grey explores the history of copyright, using the only slightly less alarming headline Copyright: Forever Less One Day (there's also a transcript at that page).
Copyright is an important system; it underlies much of the commerce I do every day. And its current implementation is basically cuckoo bananas, due in large part to exquisite lobbying by well-connected corporate interests. If you have five minutes to learn a little history (and have a few chuckles at George Lucas's expense), check this out:
See also: Everything is a Remix.