And if you happen to be running ubuntu 12.04, then keep in mind that apt-get install ruby-bundler will pull in the wrong version, so just install the ruby1.9.3 package, and install bundler, posix-spawn, therubyracer and execjs via 'sudo gem install'. After that the youtube comments work just fine.

Took me only 3 hours to figure it out being a total ruby noob. So easy.