You can't do live streaming using the video tag on any browser except safari (which supports the Apple live streaming protocol). The only container formats supported by the popular browsers (mp4 and ogv) require that you know the locations of all of the keyframes that will appear in the video ahead of time. In order to have live streaming in the browser they'll have to support a streaming-friendly container format like mpeg-ts.

thats totally wrong. you can do WebM live streaming that works in Firefox, Chrome and Opera. Ogg Theora with Icecast also works in Firefox, Chrome, Opera

But not ie9. And I don't believe they support playing h264 video in a webm container, so you either have to write your own broadcasting tools or transcode everything to vp8.

you can do WebM and/or Ogg Theora live streaming with Flumotion, Icecast, GStreamer. This just works in the video tag in Firefox, Chrome and Opera. It does not work in Safari and IOS since Apple refuses to support those formats.

Yes. I believe the Business on Software conference 2011 used one.