Facebook has been following comments and posts that are not published by users in order to see what thoughts don't make it onto users public pages. The company claims that they are interested in knowing what people don't post so they can improve their system to encourage them to make those posts. They call this behavior self-censorship and want everyone to stop doing it, they claim the non-posts take value away from Facebook.
The fact that they are doing this is scary and crazy, remember Facebook has been sharing data with the NSA! We have all written posts and then decided against posting them for various reasons. Now we learn Facebook is looking at these posts. If they choose to save them as they claim their policies enable them to, it could mean that every key stroke entered at Facebook could be sent to a government agency.
On top of all this is the fact that users chose not to post these comments so they should not be seen by anyone. This is a breach of privacy that goes beyond user-beware, as users don't even know their posts are being viewed.