This is a case for an entirely different protocol XMPP and how to scale APIs with frequent updates, which some services get around by polling.

If scaling API calls is the problem you are trying to solve I would still use HTTP with persistence, session "liveness" and push updates.

Using jabber may be a quick solution but it may not be right tool...

I talked to Rabble after the talk and he did say the "beyond REST" was meant to be tongue in cheek because he Kellan believe XMPP should supplement a RESTful interface.

That said this content is great because it really solves a whole bunch of issues with a regular RESTful interface, mainly around the issue of the client/server model rather than server/server.

Both Kellan on Flickr and Seth/Blaine are going to be implementing this soon and I'm really excited to see what the concrete implications look like.

This idea has (IMO) a better name, WebHooks, and a standard place for discussion about the issues and tools around the concept: http://webhooks.pbwiki.com/

XMPP unfortunately ends up being the "heavyweight" solution; there's probably a decent argument that WebHooks are to XMPP what REST was to SOAP.

(And don't get me wrong, what I'd really like to see is websites that support RSS, WebHooks and XMPP, each has strengths and can compliment the other)

What about PING, isn't it already a kind of push standard for blogs? The only thing missing is the ability to request pings, currently only the blog admin can add ping recipients.

Not quite the same. That's an update, this is a callback.

Oops - I was thinking pingback/trackback.

Yes, you are right. This would be a lot like registering for a short-term ping subscription.