So there's two different concepts. One is original creative output, which is copyrightable. The other is information, which is not copyrightable. If you find s

So there's two different concepts. One is original creative output, which is copyrightable. The other is information, which is not copyrightable. If you find something verbatim identical in a bunch of different places, you've got a strong case that it's just information, because if it were original creative output it wouldn't show up identically in multiple places. If it turns out everyone was plagiarizing a single source, but you were unaware and took down the offending content when asked, you won't have much in the way of legal liability.