I believe that they haven't intentionally changed privacy settings, but in the frequent privacy overhauls it's inevitable that they break stuff and throw people's data out to the world. They need to stop thinking about innovating and thinking about how to stabilize. Facebook was perfect from a user perspective... 3 years ago. Innovation is at this point antithetical to the social web. It's why Craigslist, despite a no-frills interface, remains dominant.

Stability and user control are primary. Facebook is unstable (in the sense that its interface changes every other month) to the point of being completely uncontrollable by the user.