I'd mused about infinite copyright duration a few weeks ago, and again over at the EFF last week. Turns out there's an excellent science fiction treatment of the idea. If copyright's duration is infinite, bad things happen.
The story is very short - no more than a five minute read. I'm not going to excerpt as the best bits are spoilers. Just go read it.
HT: Paul Norvell
Update: the link above is dead. This one works. Or, search "Melancholy Elephants".