Such changes to Facebook and other social media might be bad for society because they reduce our ability to keep our private lives private. We are currently seeing, in the scandal involving David Petraeus and General John Allen, how electronic communications make it hard for anything to remain private. The sorts of changes described here arguably contribute to this problem.
If Facebook makes it harder to untag ourselves in pictures and if it makes it easier for other people to see our pictures, it reduces our ability to remain private. We might be tagged in pictures in which we are doing things that would look bad to a potential employer. Before social media, these activities would have been our own private business and would never have come to the attention of any employers. With Facebook and these changes, that is no longer the truth.
We need to have private lives. If these sorts of changes proliferate, this becomes more difficult. That is, arguably, bad for our society as a whole.