I've encountered this before. I've encountered actually on mobile devices. YouTube gives content providers the ability for their content to be limited to only platforms that can be monetized. Here's an article on it: http://support.google.com/youtube/bin/answer.py?hl=en&answer=2453875
You'll note they listed some apps that aren't monetized. Therefore, they'll be blocked from viewing the video, but it'll still come up in search results.
My new 7150 Samsung 3D Smart TV YouTube app won't play most search results. Video Not Available message appears many times as it scrolls through videos looking until it finds one it can play by that artist. Hard wiring does not help. Trying Youtube from the web browser does the same thing. Samsung help line technician had no clue their TV's did this or what the problem is.
My Friend's Panasonic Viera works flawlessly on the same search. Interestingly, my same friend has a Samsung Smart TV also, and his Samsung does the same thing mine does. Does anyone know what Smart TV's out there work properly? Sharp, LG?