'will' you are wrong. youtube do use streaming that's why they've recently invested in the ripcode's streaming hardware.
you are also wrong about download rates. when you stream via rtmp you only download/pay for the portion of the video that you watch, scrubbing backwards and forwards makes negligible difference. becuase when you arrive at your destination point it does not download the rest of the video, it only downloads what you actually watch.
the opposite is true with progressive download, you may only watch 30seconds of a ten minute video, but download the whole file during that time.
therefore you use far less bandwidth with rtmp streaming servers than when using progressive download as most people do not watch the whole of the file they click play on.

sorry bk, you don't know what you are talking about. YouTube uses lighttpd, you can see it in their headers.
Every RTMP streaming server that I have ever connected to downloads the whole video and re-downloads the whole video and re-downloads the whole video.
[B]HAVE YOU EVER TESTED ANY OF THIS?[/B] I seriously doubt it, or you wouldn't be spouting such BS!