http://www.newsweek.com/black-profile-pictures-some-facebook-accounts-what-do-they-mean-1145349

The blacked out photos some Facebook users replaced their usual profile photo with Sunday had nothing to do with the latest security breach on the website. Those with blacked-out images actually changed them to raise awareness around an issue. 

The blackout was prompted and spread by a message that was being sent around the site among women looking to show what the world might be like for a day without women.