Facebook and Google are battling it out to dominate your smartphone time and, for now, Facebook is winning. According to the latest stats from comScore, Facebook was the most popular mobile app in the United States in 2012. The Google Maps app held the top position until October, when Apple rolled out its latest mobile operating system, iOS 6, and replaced the built-in Google Maps app with its own, less accurate version. Of course, Facebook also had a hand in its own success. Its number of monthly unique visitors rose steadily over the course of the year. In August, the company rolled out a long overdue revamp of its iOS mobile app for iPhone and iPads, significantly speeding up the launch, scroll and browsing times. User reviews in Apple's App Store shot up as a result, and in December the company followed up with a better version of its Android app. Facebook started 2012 facing criticisms of its mobile strategy, and while there are still lingering questions about how it will make money off of mobile, these stats show its adept at transferring the Facebook experience to tablets and smartphones. People aren't just opening their Facebook app the most, they're spending astonishingly large chunks of time in the app, poking around and reading up on their friends. The social network's app was the single largest, single app time suck, accounting for 23% of the time people spend using mobile apps, according to comScore. Instagram was a distant second accounting for just 3% of the time people spend in apps. Google's app with the most engagement was Gmail, but in total 10% of users' time was spent across various Google apps. The more interesting story in the coming year might be Google's rise to dominate all mobile platforms, not just its own Android operating system. Facebook may have the No. 1 spot locked up, but Google apps account for the next five most popular apps. After Maps, Google Play, Google Search, Gmail and YouTube were the top apps on Android and iOS devices in December. Google only re-released an iOS version of its Maps app in December, which could continue to fight back and possibly overtake Facebook in 2013. Apple's only app on the list is iTunes, coming in at 8th place. Rounding out the top 10 list are Pandora Radio, Cooliris and Yahoo! Messenger.