Actually that very much scares me. What's to prevent any company from copyrighting a small passage of code and then rigorously suing everyone and their brother for it? At least with patents you can claim prior art.
> "... two authors may own copyright on two substantially identical works, if it is determined that the duplication was coincidental, and neither was copied from the other."
> "Infringement requires... that the defendant copied the protected work... if two individuals both create a story that by pure coincidence is nearly identical, but each without knowledge of the other, there is no infringement since there is no copying."
Independent creation is a strong defense to copyright infringement. Compaq famously did this when they duplicated the functionality of the original IBM PC firmware, by using a strict "clean room" process. Even though numerous segments of code were no doubt duplicated, because there is often a single best way of writing hand-optimized assembly language, the provable independent creation made it a new work under copyright law. As far as I remember, IBM didn't even bother to sue.