Like the time I "hacked" into a friends daughters bank account (with their consent).
Date of Birth - Look up last birthday photos, worked out from there,
Mother Maiden name - Easy, they had anniversary photos and from their, found Mr X married Miss Y on this day, type posts,
Town of Birth. - Right there.
Couldn't find first pet,
Found high school,home address, interests, movies, books and on and on.