Meanwhile, in the land where it’s entirely the fault of the users:
“By default, messages from friends or friends of friends go into your Inbox. Everything else goes to your Other folder,” Facebook spokesperson Meredith Chin said in an email. “That is likely where the messages are being sent from other people’s emails. Even if that person is friends with them on Facebook, if the friend doesn’t have that email on their Facebook account, the message could end up in the Other folder.”
By default, the “Other” folder does not send notifications. Facebook has managed to further break email. Bravo.