Due to changes at YouTube, livestreamer stopped working, please issue the following command either at piShell or ssh and they should start working.
sudo sed -i 's/player_embedded/detailpage/' /usr/local/lib/python2.7/dist-packages/livestreamer/plugins/youtube.py
OR, update the player software to 1.9.8.
In 1.9.8, you can select the option to use "youtube-dl" program to play YouTube videos under Settings Tab. This plays protected videos as well.