http://www.nytimes.com/2014/06/30/technology/facebook-tinkers-with-users-emotions-in-news-feed-experiment-stirring-outcry.html?ref=technology&_r=0

Facebook has made repeated missteps in regards to user's privacy and information over the course of the last few years.  Apparently, they have learned relatively little in terms of how jealously people regard their privacy.  While it would seem that they didn't do anything wrong, per se, the optics of yet another privacy brouhaha for Facebook are certainly negative.  Of course, given the Facebook's sheer size, it seems unlikely that this will actually shift behavior for its users.