(Updated) Facebook is now a mobile company, not just in culture, but in audience.  During its Q4 earnings announcement, Facebook said its mobile active users surpassed the desktop for the first time in its history — 680 million users (+57% YOY) out of 1.06 billion overall.

But perhaps the most surprising data point is the skyrocketing number of mobile-only users. “In only a year, just under 100 million more people starting using Facebook only on mobile, never touching desktop,” explained The Verge reporter Tim Carmody.

This should startle journalists for a couple reasons. 

First, Facebook’s mobile footprint eclipses every news organization on the planet, and a huge population of users are growing accustomed to consuming mobile news on Facebook.  It accounts for 23% of all time spent with mobile apps, according to Comscore in December. That beats every news organization’s app combined by a long shot. A study by Flurry in November found that the news category only accounts for 2% of total time spent on apps. Social apps accounted for 26%.

Twitter is also forming mobile habits around real-time news consumption, and the sky is the limit if it can solve the discovery problem. By creating platforms tailored to mobile — not just extended to mobile — these social giants are grabbing a huge share of attention, limiting the mobile opportunity for news organizations.  And as we learned from the shift from newspapers to the Internet, catching up is very difficult.

Second, Facebook’s numbers hint that there’s a shift among a growing audience from desktop-centric behavior to mobile first.  By extension, desktop consumption will decline.  Google is already seeing it: four straight months of a decline in desktop search (Google expects mobile traffic to surpass desktop later this year.).  While both Google and Facebook are monetizing this mobile shift — they dominate a large majority of all mobile ad dollars spent — news organizations are not. 

At least yet.  And simply shifting display ads to mobile is not the answer.

That’s why I’ve been pounding the drum for news organizations to throw ourselves at mobile, tripling the investment and shifting our newsroom cultures to “mobile first.” (See my earlier post, “Why mobile will disrupt journalism like the Internet did a decade ago.”)  After all, the mobile revolution isn’t coming; it’s already here.

(Full disclosure: I’m GM of Breaking News, a mobile-first startup owned by NBC News. Here’s our approach to mobile.)