Just a personal story to bring one example into focus.
I got sober 8 years ago and never talked about it online until I was about 4 years sober. Never saw a single promotion for anything related to alcohol…
Until the day I made a single comment on Reddit telling my story to help support another person who was just starting their own sobriety journey.
And like magic, all promoted communities to me were alcohol related. Even though I’m an ublock user, when I would selectively disable it every advertisement I saw online was related to booze.
So even though there are ethical applications for my data, I found that it was used in an attempt to target me based on human frailties.