As an author and former journalist, I thought I was pretty well versed in the fair-use defense. I thought that any short quotation from a copyrighted work is protected under fair use, and I always assumed that a single line from a song would easily qualify as a short quotation.

But this article (and the article it links to, "Never quote a rock lyric in a book unless you're rich") suggest that you can be held legally liable for quoting even a single line from a song without permission.

That definitely seems to go against the spirit of fair use.