[randallu]

They stipulated that the player use HTML5 so that it could show all of their ads and overlays correctly. That seems pretty reasonable.

Microsoft couldn't have just the player in HTML5 because their embedded webview can't play video -- which is where the stories of "Google wanted the whole app to be done in HTML5" came from.

IMO an embedded webview should be able to play video, or Microsoft should have been able to get something together just for youtube.