In many jurisdictions there are certain people called mandatory reporters. These are people such as educators, foster parents, medical professionals, social workers, police officers, etc. who by virtue of their training and positions of authority over other people's children are required by law to report suspected child abuse, or risk prosecution themselves. Many of those same mandatory reporters will be attracted to this site.
I would hope no one would be stupid enough to post evidence of abuse on a public forum, but I met some pretty dumb parents when I was a foster parent, especially when they are under the influence, so it wouldn't surprise me if it comes up eventually. Do we have a specific process for making these sorts of reports that have fallen out of the realm of normal moderator duties and into legal issues? This is especially tricky with an international membership as to what jurisdiction should be informed, etc. Should this be addressed in the FAQ, or is it just so extremely rare as to be handled on a case by case basis should it ever come up?