I use my Nexus 4 with a Google Apps account outside USA. There's no YouTube option in my GApps dashboard, as confirmed by this support page:
YouTube is not an available service for Google Apps in countries where YouTube has not yet launched. If you're a domain administrator in one of these countries, you will not see the option to enable YouTube as a service with Google Apps for your domain in your Google Apps Control Panel. http://support.google.com/youtube/bin/answer.py?hl=en&answer=1074205
I can visit YouTube in the web browser and that works fine, although I can't sign in. (I might be able to sign in with a dummy Gmail address but that would defeat having a Google Apps account.)
When I launch YouTube app on my Nexus 4, it promptly shows a banner "signing in..." but for the reason I just mentioned, this never finishes.
Does this mean I will never be able to use the YouTube app?! Does this really cause me to be completely locked out of YouTube on Android? That can't be right!