The increase in mobile usage has resulted in its daily user base expanding more quickly than the number of advertisements it delivers, Facebook said in amended S-1 filing with the Securities and Exchange Commission Wednesday.

"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 states.

Facebook that it planned to buy Instagram for about $1 billion in cash and stock. Competition experts believe the deal will ultimately be approved, the FT reported.