YouTube BBcode not working properly
 

When I looked through some posts, I noticed people on my board were using my YouTube BBcode wrongly.

It's intended to work like this: (with the video ID)
Code:
[youtube=Road Warrior]VfBe4wicyo0[/youtube]
Strangely enough this also works: (with the embed code)
Code:
[youtube=Road Warrior]



[/youtube]
Now, I don't know if it's YouTube's fault of vBulletin's fault. If it's vBulletin's fault, how can I prevent my members from using these embed code's instead of the ID's?