None of the previous replies addressed this question, so I think it's unfair to downvote this.
As I see it, Facebook could at least attempt to act like they have the user's best interest at heart. This means actively educating them about privacy, risks, and not setting defaults to public. Also not everything on private as this would confuse some people, but at least use non-public and reasonable settings. And/or have a public discussion about it.
Facebook is becoming ubiquitous enough that it's almost something like "internet" or "calling" in general. For such services we have made laws, e.g. in the Netherlands there is a net neutrality law, and sending spam is illegal. But for individual website we have no laws, nor do I think we can make any in the near future without a huge lot of fuzz about it. I'm not saying governments should make laws for Facebook to follow, I'm just saying it won't any time soon, if at all.
So then how do we make sure such a big service acts in our best interest? I think Facebook should start acting less like a for-profit company and more like a government would. Not with elections per se, but at least act in the public's interest instead of working against the users.
And that is how I'd answer the question of "how is this Facebook's fault?". Being a popular for-profit company is not a 'fault', but with so many users they have a responsibility, and I think that it's fair if we, hackers that understand the technology, try to make them act responsibly.