Facebook's XMPP gateway, long officially deprecated, doesn't appear to work anymore. https://bugzilla.mozilla.org/show_bug.cgi?id=1236133#c0
Need to apply, https://hg.mozilla.org/comm-central/rev/4f1b3e5af8ef and adapt for #13323 (closed).
Also, close down #17464 (closed) and remove all the places we mention Facebook support (project page, faq, etc).
On a brighter note though, I believe there's a libpurple implementation, so hope that a JS prpl will emerge, and someone on IRC was mentioning working on it during GSoC.
The new protocol is based on mqtt.