The only thing they'd need to do is fill in a username and a password field, and use any client, web, app, desktop, anything, but no, because Facebook is there, it's pre-installed on phones.
What happened to the idea of belonging to a group, to something? To express identity online? How do I move people?
I'd be willing to run mail and XMPP on their domains, because some of them still has a website, but it doesn't seem to interest anyone.