The social login is not new -- they've used it for location verification for a long time, if you suddenly log in from, say, another town within the same day. My pet peeve is that some profile pictures don't contain actual faces, and some tagged pictures are tagged incorrectly -- so sometimes there's no way to correctly ID a person.
You are allowed a few misses, but it calls for (a) Facebook to perform facial recognition to make sure the pictures they show at least show recognizable faces, and (b) for us to prune friends list to keep only those contacts whose profile pictures we recognize (either because it's their actual face, or because one knows them well enough to recognize silly non-facial logos)