To start off with I was mainly against LulzSec, but after going through some of their posts it does make sense. It is evident that most businesses didn't take security seriously, and although there is no real way to prevent against DDoS attacks, there ARE ways to block out direct hacking attempts to steal information. Would you honestly rather, for example, someone from Al-Qaeda being able to sit inside the CIA for months at a time and get data about who or where they're planning on striking?
It may not be the most diplomatic way of notifying people of breaks in their security but after smaller sites being hacked it looks to me like the sites with more responsibility either don't have enough respect for what hackers can do or don't take the matter of security easily enough. Is it really that bad that they took down this site for a short time, or that they got a bunch of passwords AND THEN TOLD US EXACTLY WHOSE PASSWORDS THEY HAD?