Though my recent posts on the subject have been a bit one-sided, I have to share my favorite example of copyrights being used to suppress (or at least attempt to suppress) creative output.
In 1994, Saul Zaentz, the man who had acquired the rights to the music of Credence Clearwater Revival sued John Fogerty for plagiarism because a song on Fogerty's latest album (which Fogerty wrote, played and sang) sounded like a CCR song (which Fogerty also wrote, played and sang). In other words an artist was basically sued for sounding like himself.
Zaentz lost and had to pay the court costs, but if Fogerty hadn't been a famous rock star with a new hit record on Warner Bros., how for do you think he would have gotten?