Youtube sure works on Smart TV, as long as your smart tv build in with youtube function. Input text with your smart tv controller is a pain, by pointing the soft keyboard button one after another.
While following the Malaysia airlines MH370 missing news. I am trying youtube on a LG Smart Tv. I notice how youtube works on LG smart tv. Instead of input your name and password through the software keyboard, you login the youtube on LG smart tv with mobile phone (or desktop).
When you login youtube on LG smart tv, the system provide an access code, and ask you to access https://www.youtube.com/activate. You activate your device (the smart tv) with the access code provided on the web. The LG smart tv will automatically login for you.
Finally someone has made the process right.
In mobile and PDA, the 4 basic apps are calendar, contact (address book), todo list and notes (memos). In smart tv the basic apps should be video (youtube), photos (flickr, picasa etc), music (iTunes?) and ... let the smart tv vendors figure out the rest.