Its clear that when Facebook said it was going to be a mobile-first company back in 2013, it meant it. Its now surpassed 1 billion active mobile users a month, which is about a 34 percent increase compared to a year ago. Sure, a lot has happened in the land of likes in the early part of 2014 — it spent close to $19 billion for WhatsApp and another $2 billion for Oculus VR — but its primary source of income for the year still comes from good ol advertising on its core product: Facebook.