Facebook was also a gateway like slack, but not as good as slack's gateway.

Google Talk was real and federated XMPP before they killed the product.

> Google Talk and Facebook Messenger were XMPP all the way through and worked with vanilla XMPP clients

I remember this, it was great to connect to absolutely every chat platform with bitlbee and pretend that all my chats were just DMs on some irc server somewhere