I've long advised clients about the importance of including proper notice on their works. As a practical matter, you should do everything in your power to make it easy for someone to get in touch with you for permission (and payment) to use your copyrighted material. As a matter of law, however, proper notice—especially when you also embed it in your metadata—gives you some important legal tools. Yesterday the 5th Circuit Court of Appeals issued an opinion that elaborates on one of those tools: the ability to foreclose "innocent infringement" claims by unauthorized users of your work.