They've got a billion-strong userbase and yet the Android app still dumped literally every attachment I received into my camera roll until I manually added '.nomedia' files in the right places.
And, oh man, the API for businesses is a Kafkaesque nightmare. Maybe it was good before it got Zucked, but I had to fight with their support for over a week to get an automated ban-hammer overturned... only for it to get auto-banned again two days later. We hadn't even deployed the damn thing yet!