you and tube on its own are not, but combined, as in "youtube" might just well be a problem.
Google owns youtube, and as far as i am aware they don't allow the word "google" to be used in a domain (atleast so i have been told recently)
So i would imagine they wouldn't like the word youtube being used either.
It might pay to atleast enquire about it anonymously, just email them explaining your situation and that you are planning to purchase a domain with the word youtube in it.
