[Steuard]

I'm not a lawyer or any sort of expert on copyright law, and in particular, I know that I can't comment on things like whether there's a minimum level of creative effort necessary to merit copyright.

That said, my understanding is that when you write something that's eligible for copyright protection, it is automatic: you don't need to say "Copyright" explicitly at all. It doesn't matter how you use the work in question (although the protections for "unpublished" work are stronger than for "published" work).

Now, it sounds like one element of this trial involved the license implicitly granted to Twitter by posting there. But the very fact that licensing was an issue demonstrates that copyright was in force here. (And the trial evidently concluded that Twitter's license is not tantamount to placing content into the public domain.)