> In the case of a published work, a notice may prevent a defendant in a copyright infringement action from attempting to limit his or her liability for damages or injunctive relief based on an innocent infringement defense.

I think this is the big one. Copyright infringement can be a criminal or civil offense, and the civil offense can be "willful", "ordinary", or just "innocent". The more that a defendant can show that he didn't realize he was violating copyright, the more the offense could be pushed towards ordinary or innocent. A big fat copyright notice makes it hard to make that argument.