Google on Tuesday announced that videos on YouTube were collectively played more than 1 trillion times this past year. In its look back on the year in YouTube videos, Google revealed that it served more playbacks than ever before in 2011. To quantify the massive figure, the company noted in a blog post that a trillion playbacks represents about 140 views for each person on earth, or more than twice the number of stars in the Milky Way galaxy. Hit the break for a quick countdown of the 10 most popular YouTube videos of 2011 hosted by none other than Rebecca Black.