Facebook Better Get Mobile Quick. 102M People Accessed Solely From Mobile In June, Up 23% Since March

There's a staggering new statistic in Facebook's 10-Q SEC document today: 102 million people accessed Facebook solely from mobile in June, a massive 23% increase over the 83 million mobile-only users in March. 18.7% of its 543 million monthly mobile users don't even visit its desktop site. That means if it can't make its mobile advertising generate a lot more money within the next year, revenue could plummet like its stock price, down 6.2% today to $21.71.

Another dead-serious new stat is that Facebook only grew 10% to 168 million in the US this last year, compared to the global average of 29%.

There were bright spots in today's 10-Q, essentially a deeper version of Facebook's earnings report. Facebook only spent $24 million to acquire Tagtile, Glancee, Lightbox, and Karma

Another positive was that Facebook's monthly users in Brazil grew 146% this year to 54 million and India was up 84% to 59 million. That shows that in key emergent markets, growth is still strong. Unfortunately users don't monetize as well there.

In the US where Facebook commands high ad rates, it seems to be having trouble signing up and retaining the last 80 million or so Internet users, as it only added about 15 million users in the last 12 months.

But most troubling is that more and more users are ditching Facebook on their computers where it can show up to seven ads per page. Instead they're accessing through their phones and tablets, where it only shows the occasional Sponsored Stories ad.

The 10-Q noted "During the second quarter of 2012, the number of DAUs using personal computers was essentially flat, and declined modestly in certain key markets such as the United States and Europe, while mobile DAUs continued to increase." And studies show that Americans who use both interfaces spend more time on mobile.

Facebook finally started showing ads on mobile at the end of February, but five months laters users only see the occasional Sponsored Story there. Those social ads may receive as high as 13 times the click through rate of Facebook's desktop ads,and Sponsored Stories as a whole are bringing in $1 million in ad spend per day, $500,000 just from mobile. Still, it can't show nearly as many per session. Facebook CFO David Ebersman explained the company's first earnings call that "We're being very careful about the volume of sponsored stories in the news feed because it's so core to the user experience."

For years Facebook has tried to minimize the presence of ads on its site. But those were different times, when it was a private company with a desktop user base and plenty of room to stick ads in the sidebar. But right now it must come to grips with the fact that it could have to support itself with mobile ad revenue, and that means putting plenty of ads front and center.

Postscript: With further thought, I'm not sure Facebook will be able make enough money on mobile ads alone. It would simply have to cram too many into the feed, and that could wreck the user experience it has spent years building, and lead people to visit less. It may need to figure out how to realize the potential of gifting startup Karma that it acquired in May, and get into other mobile revenue streams such as payments if it wants to get back to its IPO valuation.