I'll just leave this here http://mobisocial.stanford.edu/papers/hotpets11.pdf First sentence of the abstract: "This paper proposes Mr. Privacy, a social application framework built on top of email..."

Wait, wasn't RSS invented to replace mailing lists (aka news letters)?

But yeah, making a facebook/twitter-style social network app that uses plain email as transport would be really cool.

> Wait, wasn't RSS invented to replace mailing lists (aka news letters)?

Probably. On the server-side RSS is nicer in some respects - you're not sending out mail to old, disused inboxes, you don't have to manage subscriptions or worry about being blocked as spam etc.

One thing that I think might make email better is if people got used to the idea of "email apps". The idea that my inbox might collate stories from a given source into a scannable digest (like RSS might give me) seems like a strange departure from the traditional idea of what an email client or service is "meant to do" - present discrete, unmodified messages in the most transparent way possible.

For a social network it's clear that you'd need something like that, though - you'd need clever filters on your feed, thumbnails on images, possible integration with image-sharing services etc etc. Using email and mailing lists gives you a big head-start, but if you can't build on top of it then it can't take off like a dedicated protocol can.

XMPP has this neat feature that allows you to know what features are supported by a remote client, allowing you to just send social stuff to online clients that want it. Email doesn't have this, but it could be approximated by some clever use of multipart messages. It'd be even better with filters, but you can't count on things like sieve being available.