There’s something in Facebook’s Q4 report that made investors nervous. The stock initially fell 7% in after hours trading before recovering to be virtually flat after the social networking company reported Q4 results that topped forecasts. Not including one-time expenses, net earnings came in at $426M, +18.3% vs the last three months of 2011, on revenues of $1.59B, +39.9%. The revenue figure is ahead of the $1.53B that analysts expected. Adjusted earnings at 17 cents a share also beat forecasts for 15 cents. The social network company says it had 1.06B monthly active users at year end, up 25% from the end of 2011. About 680M of the users accessed Facebook on mobile devices — making this the first quarter in which the company reached more people on mobile gadgets than on traditional computers. Ads accounted for $1.33B of the total revenue and were +41%. About 23% of the ad sales were for placements on mobile devices, an increase from Q3 when they represented 14% of ad sales. That should reassure investors who feared that Facebook would infuriate users by trying to squeeze ads on to the limited screen real estate on smartphones and tablets. “In 2012 we connected more a billion people and became a mobile company,” CEO Mark Zuckerberg says. “We enter 2013 with good momentum and will continue to invest to achieve our mission and become a stronger, more valuable company.” Facebook closed Wednesday at $31.24, below the $38 the company commanded last May when it went public but up from the low price of $17.55 that it hit in September.