I think copyrights are a bad thing. That being said I think most thing that are posted without mention of the author or even those who mention the authors but are just pure and simple copy paste, I think it's a good thing we down vote them. I would even love to see even better mechanism to counter those kind of post but this isn't because I "believe" in copyrights. I don't think copyrights are useful for humanity. I'm not the only one making this case. Dan posted on the subject already. He posted the first chapter of a whole book on the subject making the case that copyrights are not serving us.

As for looking for post with copyrighted image, I think if it's a post only of those type of images with text then they should be downvoted but otherwise, if there's original text then I don't think they should be downvoted whether or not a link to the original author is provided.