It's been asked about quite a fair bit, and, well, it's back now; only a bit different - but better to some extent.
Example:
Quick How-To:
Input the following BBcode into your post.
[code][youtube]YouTube Video ID[/youtube][/code]
And include the ID of the YouTube video you would like to include the [youtube] [you-tube] tags. The ID is the series of random alphanumerical characters (or string) in the URL directly after the "youtube.com/watch?v=" part. A typical YouTube video ID would be: "pnRVIC7kS4s"
Feel free to test this in a response to this thread. First person to post a RickRoll video can have 100 rep.