I'm curious; what if you as a writer for El Reg were to receive some of these documents - what would you do with them?
It's a good question and -- with the understanding that I don't speak for The Register or its management -- the answer is that it really depends. I don't know what kind of information they supposedly stole. TFA says the files were named after Supreme Court judges. That tells me nothing. The information, if verifiable, might count as proof that a hack actually took place, but if someone shows me the cell phone numbers and home addresses of all the Justices, that information wouldn't itself be news.
In a broader sense, though, let's suppose we were the recipient of some major, Wikileaks-style information dump. What would we do? All I can say is that:
A.) It's a topic that has definitely come up in the newsroom before, on numerous occasions.
B.) In some cases things can be a little dicey for us because, being a publication based in the UK, we are subject to UK libel laws, which are notoriously backwards and archaic.
C.) Similar things have happened. For example, there are a fair number of tech-savvy people on staff. So if a story comes up that somebody stole a couple of gigs' worth of emails and "released it," one of us just might be sharp enough to figure out that there must be a torrent of them out there somewhere, and go fetch them. Fine; now we're sitting on a big pile of data that was illicitly obtained from the source. Is the leak already the subject of an investigation? Or litigation? By law, are we now complicit in the original crime? Do we then mention that we have reviewed the documents and that they are of such-and-such nature? Or do we just use the download to verify, for our own satisfaction, that the leak is in fact legitimate? If we mention that we have the documents, where do we say we got them from? Who is our "source"? If a Julian Assange steps up and offers something and says "I released this," that's one thing, but if an anonymous script kiddie just puts something out there it's a little different.
So I guess in summary, all I can say is that it depends. It depends on how important the story is. It depends on who is offering the information. It depends on the nature of the information, e.g. does it involve individuals, governments, etc.? It depends on who might be damaged by the release of the information, and to what extent, as well as how much public benefit there might be in releasing it. The answer is always going to vary on a case-by-case basis -- but where the very tricky cases are concerned, we do have lawyers we can ask.