At the phoneix forum they spent quite a bit of time talking about filming in HD in one of the sessions. At the time, Playboy was the main company doing it. Supposedly if you ever want your stuff to appear on PPV they will only accept it now if it is in HD format. I think the HD format for computers is a very loose idea and the term tossed about too freely.

There are hardly even any mainstream HD videos for computers. I watch all the stuff in the Quicktime HD gallery.. but there sure isn't very much of it...

http://www.apple.com/quicktime/hdgallery/