It seems Jeff doesn’t quite understand copyright, himself: Creative Commons is a licensing scheme*, not a ‘digital copyright’ (the term doesn’t even make sense). The fact he never registered the copyright formally means he doesn’t have the paperwork the web host is demanding, and it might also have repercussions if he ever has to sue anyone over his copyrights.
*Creative Commons is based around the idea of building your own license for an artistic work (but not software) by picking license elements from a short list. You can pick Attribution, Non-Commercial, No-Derivs, and/or Share-Alike, which are defined rigorously but basically mean everyone who uses the work must credit you (Attribution), nobody can sell the work or make money off of it (Non-Commercial), nobody can make derivative works (No-Derivs), and nobody can impose additional restrictions (Share-Alike). You can pick any or all of these terms for your specific license.
The idea of a web host proactively doing shit like this is absurd. It certainly doesn’t demand copyright paperwork for all of the content it hosts, and all of that it copyrighted just like that music. (Excluding the likely minuscule amount of public domain content it hosts.) The only thing it could possibly say in its defense is that it thought the works might be stolen. That isn’t its place. That whole line of reasoning is stupid beyond belief: Does a storage locker company seal your locker if the owner thinks you might have stolen goods? No. He waits for the police to come with a warrant and then acts based on their instructions. (Well, if the DMCA were in effect for physical goods, he’d have to act on every letter he received from someone accusing someone else of stealing their stuff. Good thing stealing music is so much worse than stealing cars: The law doesn’t demand immediate action if a car gets stolen.)