Maybe this is more of a PR move than an ethics one, considering the growing sentiment against tech giants. Facebook has developed an image of quietly doing their deeds for a long period of time, then "getting caught red-handed" all of a sudden and dragged through the media. Maybe it's about getting ahead of the curve in this regard because they believe up and coming tech will continue to deepen privacy concerns rather than plateau any time soon. Of course, it's reasonable to assume the stakes will continue to rise with the power and reach of technology, so it's a good idea to publicly appear concerned long before the SHTF. It also passes off some of the responsibility to the government for whatever disaster they think could happen.