This imo is the truly alarming takeaway. FB employees were retrieving user passwords? Around two thousand FB employees? How in God's name is Zuckerberg going to perform his usual performative contrition about that one?
I'm just trying to imagine the data structures that were being retrieved from databases. Either they stored something like a big user account data type that contained their password in plaintext, which imo is a really weird design choice, or logs for other services were being mixed in with logs leaking the user/pass combos.
Surely one of the engineers could have noticed and said 'wait a minute... those are logins' over the course of the years? We hear all the time that people want FB to follow a responsible social practices (the debate on what those are rages on, which is great imo), but can't FB at least wrangle its own code base?
On the other hand, we shouldn't take the stance that heads should roll, imo - it would just create a chilling effect that would deter other companies from ever going public about their own security mishaps.
edit: I should probably tone it down in this comment but I'll leave it for posterity