Today I spent sometime editing blog posts with embedded videos and "enabled privacy-enhanced mode". Someone told me to do so.
And I quote that someone:
We've been working to give our users more options and control over these cookies. One such option is the privacy-enhanced mode for our embed player. This mode restricts YouTube's ability to set cookies for a user who views a web page that contains a privacy-enhanced YouTube embed video player, but does not click on the video to begin playback. YouTube may still set cookies on the user's computer once the visitor clicks on the YouTube video player, but YouTube will not store personally-identifiable cookie information for playbacks of embedded videos using the privacy-enhanced mode." Google :-)