I mean, XMPP did get uptake. Google Talk used federated XMPP at one point in time. But…there’s not much money for a service provider in an open, competitive market. If you can get enough users, you want to put up walls, leverage network effect. Then you get to have a monopoly on access to your users, and there’s more money to be had. So there’s always going to be people trying to get everyone into a single provider.

I think that with email, the magic factor was that there was no one entity large enough to pull that off at the time that email became common. Today, there are actually startlingly few email service providers of the “pay me a fee, I give you a couple mailboxes” variety – I was amazed when I went looking this year. I’m wondering whether email might become a walled garden before messaging stops being a walled garden.