Nielsen:

Teens have officially joined the mobile Data Tsunami, more than tripling mobile data consumption in the past year while maintaining their stronghold as the leading message senders. Using recent data from monthly cell phone bills of 65,000+ mobile subscribers who volunteered to participate in the research, Nielsen analyzed mobile usage trends among teens in the United States. In the third quarter of 2011, teens age 13-17 used an average of 320 MB of data per month on their phones, increasing 256 percent over last year and growing at a rate faster than any other age group. Much of this activity is driven by teen males, who took in 382 MB per month while females used 266 MB.