Instagram's American users interact more regularly on mobile than Twitter's users

"Pictures beat words: In August, U.S. smartphone owners visited Instagram from their smartphones more frequently and for longer periods of time than they visited Twitter.
That data comes from comScore, via a new mobile measurement report: It says that throughout August, Instagram had an average of 7.3 million daily active users — or DAUs, in Facebook parlance. That tops of Twitter’s 6.9 million DAUs over the same period of time.
What’s more, the average Instagram user spent 257 minutes accessing the photo-sharing site via mobile device in August, the data claims, while the average Twitter user over the same period spent 170 minutes viewing.
This is the case despite the fact that Twitter had approximately 29 million unique U.S. smartphone-based visitors in August, while Instagram had just under 22 million (comScore measured usage across iOS, Android and BlackBerry OS devices that accessed both sites via native application as well as through the mobile Web browser). This stems from the roughly 110 million smartphone owners who live in the U.S."

Source:  All Things D, 27th September 2012