Can someone create a WebRTC web app in this way, so one person can broadcast to millions through P2P technology? Or would the browser vendors need to make certain API's available before they can do that?
Once arbitrary data can be sent through peer connections via a browser javascript application, then there is no reason why the BitTorrent Live protocol (or some other similar P2P streaming protocol) could not work over WebRTC.
One difficulty I see is actually getting the binary data into a <video> element. It would be in theory possible to write to the file in the HTML5 FileSystem API and point the video element to it, but that would require transmitting the stream in a way that is ameliorable to seeming like a static video on disk.
