I have to say, Facebook at work was probably the best thing I ever used for collaboration and knowledge sharing. It was so much better than slack, I never understood why people wanted this chat style for group communication.
But I think that the big learning from trying to roll Workplace out to other companies is that it was the FB culture that made it work.
It's also worth noting that even though internal-FB stuff in core FB was absolutely bonkers, it definitely contributed to community formation, as you'd end up seeing that your XFN peeps hobbies/kids etc, so there was a loss there.
Although speaking as someone in EMEA, it was totally, totally worth it.