Re: Isn't that illegal?
"Under penalty of perjury I certify that the information contained in the notification is both true and accurate, and I have the authority to act on behalf of the owner of the copyright(s) involved."
That only applies to the work that you think is infringed. If Madonna thinks that _her_ song is on your website, then she has to identify _her_ song. If she claims copyright on a song that isn't hers, that's illegal. But if the song on your website isn't hers, that's legally fine. Mistakes happen. But what happens her, sending a takedown notice for something that doesn't even exist, that should be made illegal.