The author assumes that the complexity of Facebook's privacy settings are due to a lack of attention to good design. However, the rest of Facebook doesn't really suffer from this problem nearly as much. Which is more likely: Facebook happened to design this one thing poorly, or they explicitly opted for a poor design in this one particular case? To answer that, follow the money. Why would they want to over-complicate the UI which gives the users the keys to lock down the data Facebook is able to share with 3rd parties?
The irony of the "share on" bar next to the post is quite funny.
There is nothing ironic about it. His whole point is that sharing should be something the user chooses to opt-in, which is the case with that "share on" bar.