A few stats I found interesting in the latest comScore US Smartphone Market Share Report:

Approximately 190 million US smartphone users which accounts for a penetration rate of ~77% of the mobile market. Significant growth still ahead for smartphones.
Apple was a winner in both smartphone handset market share and operating system market share growth versus February 2015.
Facebook has a reach of 70% on US smartphone users. Incredible to know that 70% of all smartphone users in the US have the Facebook app on their smartphone.