The embed bbcodes actually just read a string of text, so the user would simply enter:
[youtube]youtubeid[/youtube]
This is a GREAT security measure, as they can embed content to your site without being allowed to enter html. The bbcodes at ubbdev cannot allow a user to do anything mallicous, as it only allows text and numbers (well, mine does as it uses a regex to filter what is entered for increased security).
I have the bbcodes on my forum, a specific posting:
Video: North American Union Huge step in world government and your enslavement
