This is what I always have thought to be a huge problem in RESTful API design of all major companies like Twitter, Facebook, Google etc. It is mainly pull-technology. One has to ask the Facebook-server all the time: get a list of friends, get a list of friends, get a list of friends.

I'd love to see an API model based on events and callback URL's.

pseudo, but you'll get the idea:

http://api.facebook.com/event/on-friend-connect?callback=htt...

IMHO, WebServices should communicate in an evented fashion. If I want to draw an umbrella on myserver if it is going to rain in The Netherlands, I don't want to ask the weather server every X minutes: is it going to rain? is it going to rain? is it going to rain?

No, I want:

http://api.weeronline.nl/event/on-weather-change?location=Ut...

pubhubsubbub solves this issue for RSS feeds, but pubhubsubbub is way too narrow to me. I hope evented API's will become the next big thing, enabling developers to create a whole new bunch of awesome products.

Isn't this what Webhooks was all about? I remember they were all the rage a while back but I haven't seen much more adoption since then.

I'd love to be proven wrong though.

Ha. Now I understand why Facebook said "Google and Apple need to improve their browsers" a few days ago.