<<"The screenshot above hints at what that might look like. I grabbed it from this YouTube help page for Google Moderator on YouTube. It shows the channel settings for a YouTube content producer (in this case, obviously someone who works for YouTube). The last button, which I’ve circled above, is for “Live Stream.”>>

http://techcrunch.com/2010/06/03/youtube-live-stream/

The screenshot referred to as "screenshot above" above is below ;-))
http://tctechcrunch.files.wordpress.com/2010/06/livestreamyoutube.jpg

It would be cool to be able to broadcast to this from gtalk/jabber by starting a video call with it

DPic
I guess the service will be offered to premium partners at first, and without deep integration with other Google products. But it will be rolled out to everyone, a Gmail/Talk-Youtube feature would be great.

I wonder how users will notify their friends (I prefer the term "followers") about upcoming live streams...

Google needs an open, cross-services notification system. When Google Docs enabled the public sharing of documents, we asked for a notification feature in Google Talk to know about our friends' updates in real-time http://blogoscoped.com/forum/143782.html . Google didn't make one for Docs, because "email works" I guess, but as they start to benefit from the "follow model" with Youtube's subscriptions, Picasa's favorites and Buzz's followers, I'm sure they'll do their best to aggregate... oh, wait! http://www.google.com/buzz/117377434815709898403/JofpbgmfT5x/So-I-have-this-vision-for-Google-Buzz-Id-like

[link repaired -ianf]