Youtube embedded video: autoplay feature not working in iphone

UPDATE :

iOS 10+ now allows auto-play on HTML5 < video> elements, just have to mute the audio on elements. Youtube will still not. Android is still SOL too, but hey, its a start!

SAMPLE:

<video autoplay muted>
  <source src="movie.mp4" type="video/mp4">
  Sadly, your browser does not support the video tag X_x 
</video>

INFO SOURCE: https://webkit.org/blog/6784/new-video-policies-for-ios/

It can't be done. For various reasons (including, but not limited to data usage), Apple doesn't allow auto-playing of videos.

See the accepted answer to this question.