How is this surprising? Hundreds of confidential pages land in their lap, and they are supposed to not publish them? Come now, we all know that whatever the morality (more on that in a second), we want to read them. Of course we do. Twitter, the company that always beat you, the fastest-hottest-company that steals your press, with its pants down! If nothing else, on a human level you can chuckle.
I have a sneaking suspicion that Arrington is going to handle this with some class, if he wants to keep @TechCrunch on the suggested user list. Good test: if they get pulled, assume that Twitter is not happy with them. But everyone needs to relax. Twitter screwed up, lost a lot of data, shame on them! Hackers are a living constant, akin to the tides and gravity. Twitter, even for all your hype, basic (or more advanced security!) is a must. Any company with your status should know that it is a target.
So what to do? Read the documents, and the double your security.