It’s hard to get people to concentrate long on anything on their phones and tablets, yet YouTube seems to be the exception. The video service is quickly going mobile, with small screens making up 40% of its traffic now compared to 25% last year, Google said on its earnings call today. In 2011, just 6% of YouTube traffic came from mobile. Google’s not the only one rapidly shifting a 1 billion+ user base to mobile. To put its transition in perspective, Facebook said it had 819 million monthly mobile users (73%) out of its total 1.15 billion users in Q2 2013, up from 543 million (56%) of 955 million in Q2 2012, 325 million (43%) of 739 million in Q2 2011, and 155 million (32%) of 482 million in Q2 2010. Note these people used Facebook mobile at least once, but may also have used desktop.