You may have noticed that some youtube videos are available in higher quality. By adding “&fmt=18” to your yourtube link HQ will be the default displaysetting.
eg;
http://www.youtube.com/watch?v=mfAsibkCmZw is the normal LQ version.
http://www.youtube.com/watch?v=mfAsibkCmZw&fmt=18 is a better HQ version.
Sure you can click the switch in the YouTube window, but if you are linking why not link HQ 🙂