I think Moxie Marlinespike's talk at Defcon 18 (2010) was a really good one: http://www.youtube.com/watch?v=eG0KrT6pBPk
He talks about how we do not really have a free choice when it comes to things like having a Facebook account or having a mobile phone. Namely due to the network effect, you don't really have a choice if you want to be a normal member of society.
As repeated by resonator several posts up.
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.
If it's my goal to create a product that forces people via social pressure to do something, it's definitely my fault when it works.
Your response is the same as people saying "don't fly" when they complain about the TSA. 'Someone had an unpleasant experience with the TSA? How is that the TSA's fault? That person didn't have to fly.'
Facebook has designed a killer product that makes it really easy to use for social interaction. But Facebook is not forcing you to use it, Facebook is not forcing your friends to use it, Facebook is not forcing social peer pressure on you, and if in fact someone's friends are wholesale excluding that person because they're not on Facebook, Facebook is not responsible for the fact that someone has shitty friends that are too lazy to include that person.
This is one thing that people often miss-understand, just because there is no explicit threat of retaliation does not mean systematic coercion does not exist.