Q: Is my publication responsible for libelous quotes from third parties or libelous statements contributors make, such as in guest columns?
A: In print or broadcast media, yes. If you publish it, you are taking ownership of it, regardless of whether someone on your staff or an outsider makes the statement. This includes quotes, letters to the editor, opinion pieces written by guest writers, even advertisements.
On the other hand, in an online publication, the Communications Decency Act should shield you and your website from comments by outsiders posted on your stories or message boards. Be careful, though: the law allows you to voluntarily screen for profane or libelous comments, but if you start rewriting the comments to improve upon them, you may become responsible as a co-creator.