The filing, which is required paperwork leading up to Facebook's initial public offering later this month, warned that its current failure to monetize mobile users posed a financial risk. The filing cited efforts to improve mobile apps as part of the company's strategy.

"If users increasingly access Facebook mobile products as a substitute for access through personal computers, and if we are unable to successfully implement monetization strategies for our mobile users, or if we incur excessive expenses in this effort, our financial performance and ability to grow revenue would be negatively affected," the filing said.

The IDG News Service