@jno
// I don't think the ABer in question is with the CIA; //
That's a coincidence, because neither do I, which is why I never said it, nor meant to imply it.
//
she knows people's birthdays because they've announced them.
//
I'm well aware that this was how it was achieved and that it is a harmless leisure activity.
What I am saying is that combining AB's database of user IDs and corresponding email addresses, typically resemblant of a person's real name (sometimes stipulated as such by internet service providers) with date of birth data, gleaned from birthday threads would constitute a database of living persons which would require registration with the authorities, under the Data Protection Act (in UK, if not elsewhere).
But my main point is that name + DOB would help separate you from your various namesakes, when searching Facebook or similar, so it is information of interest to nefarious types, just as much as the people trying to protect us.