> Given there is no requirement to register a copyright, and the US is subject to international treaty commitment that there won't be a requirement to register

> Given there is no requirement to register a copyright, and the US is subject to international treaty commitment that there won't be a requirement to register a copyright, how exactly is this proof provided to a private entity? I think leaving it vague would be a feature. Somebody like Bungie it should be sufficient if the request came from somebody@bungie.net. But it seems to me if you want to run a commercial venture whose viability depends on others not infringing on your copyright you should do some legwork first to make it easily known that this is your work (I'd imagine it would make any future lawyer's job easier too). The downside is that YouTube could decide a signature is sufficient proof.