Honestly the most damaging thing Facebook has done (and gotten away with) was pushing users to post personal identifying data like it isn’t a big deal
Like the reason it was so attractive to marketers in the first place was that it had successfully convinced people it was normal and ok to post their full names and ages and all of that biz on the internet
Before Facebook, honestly a lot of us found it weird to share identifying info on public profiles
Or even post pics and tag people without asking first
Facebook has had a huge hand in fundamentally changing our expectations of privacy and I barely see this mentioned when people go on about Big Data