Facebook briefly showed a new feature dubbed "sidebar ticker," which showed all of your friends latest activity, including recent posts, activities, what they've been doing and more.
A user Tyler managed to grab a screen capture of the feature before Facebook removed it. Just based on the photo, you can see why many users might possibly be upset, the feature could be a huge privacy concern for many, alerting all your friends when you signed on.
Facebook hasn't officially posted any information about the launch of the sidebar ticker or the removal of the feature. It could have accidentally been pushed to millions of Facebook users, but for whatever reason, Facebook has removed it from view for everyone.