What keeps getting lost in this discussion is the fact that young kids are uploading videos to Youtube. That should not be allowed, both de facto and de jure. It's up to both parents and technology providers to make this all but impossible.
"Users do not need to look for videos of children to end up watching them. The platform can lead them there through a progression of recommendations.
So a user who watches erotic videos might be recommended videos of women who become conspicuously younger, and then women who pose provocatively in children’s clothes. Eventually, some users might be presented with videos of girls as young as 5 or 6 wearing bathing suits, or getting dressed or doing a split."
Holy shit, just burn it down at this point. This is what happens when you just mindlessly optimize.
This reminds me of the day I disabled Youtube history, suggestions, etc: I sometimes listen in Youtube to old civil war-era songs from my country, Spain (my great uncle was a partisan who fought against the fascists). Once I left the autoplay engaged and returned to my Youtube feed filled with current neonazi/extreme-right/conspiracy recommendations.
Retracing the browser history, it went something like: historic recordings of civil war/partisan songs -> later recordings by popular musicians of the most vanilla/famous ones -> current renditions of the old songs by extremist groups -> crazy political propaganda from those extremist groups.
As you say, it was a first hand experience of what unsupervised, mindless optimization looks like. Ethics are not factored in the merit function, so they just don't exist for the machine.
At this point I have to assume there is absolutely no-one behind the wheel at YouTube. They just set up an algorithm, check that it's increasing view counts, and did literally nothing else. Forgivable when you're an early stage startup with a small audience perhaps, but absolutely unforgivable at this scale. Time for Google shareholders to demand some level of accountability here (but while the profit is good, I guess they'll be quiet)