If a website that is not primarily engaged in massive copyright violation posts a link to a questionably copywritten work, then the onus is on the rights holder to notify.
It would seem like cases where the rights holder is unknown or has lost interest in the work (aka ophaned works) should be tailor made for this. HN has safe harbor, the rights holder has the possibility of protecting their work if they choose, and the public has access to a work that would otherwise be buried in a strictly pre-legally cleared system.
Where does our responsibility lie in determining whether something is legitimate or not? There are cases where it's obvious, and cases where it's not. What's the limit of due diligence for a casual reader?
I agree that it's unlikely. But it's possible, and certainly much more ambiguous than grabbing a torrent off some ad-laden site for a TV show you can buy on iTunes.
You call up Rutgers, and RUP tells you that they have no idea who owns the publishing rights. Copyright protection lasts far too long, and something really needs to be done about orphan works.