It's not only YouTube. We've got pornography blocked too, Flikr, Hi5 (popular among high school people)...Not to mention torrent sites, cracking and hacking.
The message you get when you visit a blocked site :
"We apologize the site you are attempting to visit has been blocked due to its content being inconsistent with the religious, cultural, political and moral values of the United Arab Emirates. "
Let's all switch to Google Video!