I think that a huge portion of the success of YouTube is not just the not having a codec issue, but the immediate start of the videos. Sites like iFilm in part

I think that a huge portion of the success of YouTube is not just the not having a codec issue, but the immediate start of the videos. Sites like iFilm in particular, were around for a number of years before YouTube, but before Flash 7, they all had buffering delays. If you remember back with RealAudio 1.0, there was no buffering, and so every time a packet dropped, the sound would cut out. The response to this was to buffer up for 15-20 seconds before starting playback. This worked ok if you knew you wanted to listen or watch something, and it was long. What Adobe seemed to realize was that you're better off starting immediately and building up your buffer as you go along. You may get some stuttering at the beginning, but it's a small price to pay for starting immediately. Starting the video immediately made YouTube addictive, literally. Shortening the time between following a link and seeing something funny makes the user want to click again.