Adobe just released a nice case study showing how Medici.tv uses the Kulabyte XStream Live 2 encoder and the Flash Media platform to deliver over 100 live concerts each year to a live audience of 80,000 each time. They launched the service back in May 2008, and have served 3.4 million free live webcasts of concerts from around the world.

If you haven't seen this experience, you have to visit their site. As soon as you reach the site, you get full-browser video with interactive overlays, that let you browse details about the concert, and search their site - without leaving the experience.  The streams are encoded from 500kbps through to 1.2Mbps from HD cameras.  The sound quality is great, and so is the video quality.