You are correct in stating that "The fact that the password was easily guessable does not make the hack right - it just makes it easy", however the problem here is that the problem goes well beyond passwords and password strength. Social networks have also made easy the ability to crack commonly used "Challenge Questions" as well because frequently your first pet's name, your school, and other sorts of information that go into comprising these questions is readily available online. Paris Hilton is another classic example of these types of challenge questions going terribly wrong as a security mechanism. You could give wrong answers to these questions, but then you are tasked with having to remember the wrong answers that you gave :)

Passwords generally exist to protect users from other users. Most hackers are using application level attacks now to compromise systems. If they have a password, it just provides a lower barrier of entry with which to compromise a system, but in many cases if you compromise an application level vulnerability you will end up with a more trusted level of access than if you compromise a more restricted user account.