[mic47]

> Facebook and Google? They use IRC internally for technical reasons. IRC doesn't fall over. Googlers internally revolted when they were told to use Hangouts internally.

I was talking about implementation of Facebook messenger, or Google hangout (which does not use XMPP), not what is used internally for communication.

Also, at Facebook, messenger is most used product internally. IRC is still used, but not that much (depends on org, infra devs use IRC more than product devs). But IRC is still essential, in case of emergencies (where you don't want to use your own product, as it may be down).