[pesenti]

We don't discard anything because we don't specifically identify or recognize these faces in the first place.

I don't think we go back to old photos, I suspect it would not be practical. But I am not positive on this one.

[plmpsu]

What do you mean by not specifically identifying or recognizing these faces?

When a face -- which is unknown to Facebook -- is found in a photo, is that face used for graph building? Is a anonymous representation of it kept?

[pesenti]

No: https://news.ycombinator.com/item?id=20903110

[nf8nnfufuu]

Don't you have to try to identify a face first, before you can decide you don't want to identify it? I don't see how it can work if you don't try to identify every face.

[pesenti]

You identify that there is a face yes, that's face detection, https://en.wikipedia.org/wiki/Face_detection, which is not the same as face recognition and doesn't need a model per person.

[nf8nnfufuu]

No I mean you have to try to recognize the face. Otherwise you can not decide whether the face is from a person who wants to be identified or not.

I don't see how it could work any other way.