In eZ Flow, the Video custom tag is not ready for working with all youtube video links.

For example, if we use a link like the following it works correctly:
http://www.youtube.com/v/koDex3KhHNM

If we use a link like the following the video won't show up.
http://www.youtube.com/watch?v=koDex3KhHNM
http://youtu.be/koDex3KhHNM

This may be because the first link will return the video in full screen, and the other two links return the complete youtube page.
Perhaps, the parsing isn't being performed as it should.

A possible solution would be parsing the youtube link to get the video ID and dynamically change the link to the supported format: http://youtube.com/v/<VIDEO_ID>

This issue has been found while progressing EZP-22029.