The claim of catching 99% of activity is really hard to justify. In many detection systems you cannot know your true number of false negatives. It's inherently unknowable in this case. A better metric would be mean time to detection for a given CEP sharer or perhaps a metric around how much CEP is shared before detection, or perhaps a metric for network size of CEP and how well FB can clean up an entire network at on…
I'm not saying online systems for catching child abuse can't be implemented. But is it really where our efforts would be most effective?
The question should be: how do you combat child abuse?
For that, we need:
1- Strong reporting systems that connect the people who in contact with children (doctors, teachers, social workers) and centralize and distribute that information. Right now, a social worker doesn't know about the doctor or teacher reports very easily.
2- Then, we need strong systems for handling the situation: i.e. social workers with effective systems for intervention.
3- Then, we need strong systems to take the children that are removed from at risk situations and place them in safe places where they can recover and grow in a healthy environment. This is the foster care system and the national health care system (or lack thereof) that will provide mental health counseling for the affected children.
Given that 1, 2 and 3 of these systems are terribly dysfunctional if not mostly broken, I'm always skeptical when people talk about social media and child protection. The situation gives me a feeling of leaders justifying the erosion of privacy and those who are authoritarian inclined supporting them, rather than people really caring about protecting children.