As described in a post by Zuckerberg, before the Paris attack it was only activated for natural disasters. Paris was the first time it was activated for human disasters and they will be doing it more in the future.
I'm entertaining the notion that this is a way to justify some new privacy-invading feature. I'd love to be wrong, and I'm open to a statement from a FB employee, if such a thing were possible.
I think the post had a bit of a frantic working backwards and managing PR tinge to it. A cyclone/tsunami also takes place over an extended period of time, and is very similar to a human disaster.
In any case, it is a really nice feature and the fact that they will start using it for more disasters is undoubtedly a good thing.
