The world's leading social networking site, Facebook, has warned investors that so far the firm's ad business is not keeping up with the shift to mobile devices.
The company's executives have been fielding questions about its mobile advertising strategy during the ongoing IPO roadshow.
Facebook flagged the potential slowdown in advertising growth in its latest filing with the Securities and Exchange Commission, The Los Angeles Times reports.
The firm said it began showing mobile users 'sponsored stories' ads in their news feed in March, but has limited the number of ads users see.
More people are accessing Facebook from mobile devices, on which Facebook is showing them fewer ads, the report said.
According to new research from ComScore Inc, the average time people spent on Facebook on their smartphones jumped to seven hours and 21 minutes in March compared with 6 hours and 31 minutes on personal computers.
Comscore measured mobile usage for Apple's iOS, Google'sAndroid and Research in Motion's BlackBerry on sites like Facebook.
According to the report, Facebook commands most of smartphone users' time. Other popular services are Foursquare with 146 minutes, microblogging service Twitter with 114 minutes and Tumblr with 68 minutes. (ANI)