Facebook's smartphone app is the most-commonly used app in the United States. According to comScore, more than 75% of adult Android and iOS smartphone owners used the social networking app in October 2013.
Follow up:Google and Facebook, two of the companies with the largest online audiences in the world, have both successfully managed to convert their huge desktop audiences to the mobile world. While Google's strategy to develop Android and make it available to hardware manufacturers for free turned out to be a golden ticket to mobile success, Facebook initially struggled in the mobile marketplace.
Today, Google and Facebook are among the most successful companies in the mobile web. According to comScore, Google's apps and mobile websites reach 88 percent of adult smartphone users in the U.S., while Facebook's mobile offerings reach an equally impressive 84 percent.
Moreover, 7 of the 10 most commonly-used smartphone apps in the United States are owned by the two companies, with Facebook's app being the most popular one. With Instagram, Facebook has another app in the Top 10, making the billion-dollar acquisition seem like a good deal after all. As opposed to Facebook and Instagram, Google's apps come pre-installed with any Android phone, explaining why 5 of the 10 most commonly-used apps in the United States are Google apps.
You will find more statistics at Statista