Tonight, Googler Mihai Parparita announces that Google Reader now sends realtime updates to FriendFeed when you share items using the PubSubHubbub protocol.
Huh-wha? you ask. Yeah, I know. It's no Google Wave. But that's what makes this exciting. This kind of small Pushbutton implementation is how real web pages will easily use existing technology to notify one another of new updates. The Google Reader/FriendFeed integration is just the first tiny step in what will be a broad deployment of realtime-enabled sites. These sites and services will let one another know when they have new data to share without the sucky inefficiencies of polling. Check out how fast FriendFeed updates when you share an item in Google Reader in the video above.
In short, it's almost zero latency.
With things like this and Yahoo's Open Strategy, there won't be a need to go to Twitter, Facebook or whatever. You'll soon be able to set it up to all come to you. This could get very interesting very soon.