Our benevolent leader has changed how the youtube bbcode works, but unfortunately decided not to tell anyone. The way it works now is like so:

[youtube]videoID[/youtube]

For example, if I wanted to post the Rap Chop video (http://www.youtube.com/watch?v=UWRyj5cHIQA), I would put this code in my post:

[youtube]UWRyj5cHIQA[/youtube]

There's also a [youtubeHD] bbcode now, which works for HD videos on youtube, not to be confused with high-quality videos.