YouTube allows other sites for embed its movies via <object> tag, e.g. see http://www.flashcartoons.org/ which has http://www.youtube.com/v/4u-30V2Lq5I?version=3&hl=en_US . Looks like the same way is used to embed video on all popular sites (e.g. facebook).
The the "Moving to <iframe> embeds"section in http://youtube-eng.blogspot.de/2015/01/youtube-now-defaults-to-html5_27.html In short, they'll deprecate the <object> embedding. What that means in practical terms is another question.
2 years ago