The problem with using youtube is that when the video finishes it, by default comes up with a page of related videos. If you are playing a promotional video the last thing you will want to do is show adverts for your competitors at the end.
How to remove youtube related videos
The solution is really simple - when you are in youtube and generating the embed code (ie click share and then embed and google shows the code) make sure that you have the checkbox 'show suggested videos when the video finishes' unchecked. For those of you who notice these things all the code does is then have an extra parameter at the end of the youtube video url - it simply adds '?rel=0' to the youtube video url within the quotes. This means it is therefore quite easy to change any youtube videos that you already have up on your site to remove the related videos display at the end.