Facebook has over a billion monthly active users on its mobile app

"Facebook followers could be forgiven for being fixated by the $2 billion deal to acquire the virtual reality company Oculus.
But another disclosure from Facebook CEO Mark Zuckerberg on Tuesday is also worthy of attention (no goggles required): More than one billion users now access the social network through mobile applications.
This milestone represents a significant shift from just two years ago, when making the leap from desktop to mobile posed a major challenge for Zuckerberg. That was the same year Facebook acquired the photo-sharing startup Instagram for $1 billion. Back then, it boasted some 30 million users. Now, the number of people using Instagram to share photos and videos has reached 200 million.
Facebook’s mobile transition is so well advanced, its services now account for 20 percent of the time people spend with mobile apps, according to a new J.P. Morgan report."

Source:  ReCode, 26th March 2014