A report released today from eMarketer projects that Twitter nearly double the US mobile ad revenues of Facebook this year, $129.7 million to $72 million. The advantage isn’t expected to last long, with Facebook’s 2013 figures projected to grow 5X to $387 million, easily besting Twitter’s $272 million. Both companies trail market leader Google by a factor of 10 and ar projected to do so through 2014. [Source eMarketer]