One thing that disappointed me in the discussion is how most was focused on whether or not the pictures in /r/preteen_girls were legal. Even if they were clearly legal, I think a strong case can be made for banning them for violating the privacy of the children in the photos.
Most of them seemed to be girls photographed at home, probably by family members. I suspect they were shared on the net with relatives, by people who did not know they were making them publicly available. There were also quite a few that seemed to be girls photographed in public who were not aware they were being photographed.
If the standard becomes to delete every picture containing people who haven't explicitly consented to that picture being posted in a public forum... well, that's a huge chunk of Reddit.
Most of them seemed to be girls photographed at home, probably by family members. I suspect they were shared on the net with relatives, by people who did not know they were making them publicly available. There were also quite a few that seemed to be girls photographed in public who were not aware they were being photographed.