This is interesting. Google still hasn't completely converted over to HTML5 video for YouTube. You've been able to opt in to the trial for years now ( http://www.youtube.com/html5 ). But it seems that more than half the videos I watch are still using the crappy old Flash player. Content wise, YouTube has way more content to convert to be able to take advantage of HTML5. I wonder if Netflix is having to convert video…
That's because of the ads. With things like ClickToFlash or youtube-dl, you notice that most videos are actually available as MPEG4 and/or WebM.