Uses for PubSub Hubbub?

I should be a asleep but allow me to brain dump here:

I'm excited about Pub Sub Hubbub. I wish it was just PubSubHub but it doesn't matter. It's a cool technology!

So here's what I'm thinking for possible uses so far:

1. decouple systems that are using synchronous messages like web services and don't need to
2. app to app push notifications without sockets left open constantly
3. it's RSS without the POLLING! how cool is that?

Think of the entrepreneurial possibilities! a FeedScrub / TwitterFeed / FeedBurner replacement / augmentation that scales faster because of reduced polling? You could do for event notifications what CloudFront does for CSS files! You could do for RSS updates what Akamai does for ads...

Think of the enterprise uses! decoupled systems pushing notifications to each other without thousands of web services calls and the necessary authentication / decoding / envelope generating etc...