Many of the Facebook users out there have been angry over changes to the privacy settings on the social network that leave their content open to more people than some want their stuff exposed to. Facebook has been working with the government to come to a settlement on charges the government brought against the social network. The charges alleged that Facebook misled users about its use of the personal data they enter on the social network.
The issue with the policy being retroactive is that it means in some instances data posted long ago was made public that was originally not public. Users complain that they weren't given enough notice on the changes before they were implemented. If Facebook agrees to this, it could have some ramifications for other online firms that use personal data of users for advertising and other things.