Honestly - so many things are grey area now with everything out on the internet.

As for the snippets it really is a matter of the content and also if that snippet link back to the source.

With everything, I would just always ask the question, who is the owner of this content? If it is clear to you who it is then better of citing it, only takes 10 seconds to do so.

That's best advice I can give as I am not an authority on the subject.