The Pew Internet & American Life Project has put out an extensive report on teens and mobile phone behavior. It's based on a telephone survey of US teens and their parents. There's lots of data and nuance but the big (and already familiar) takeaways are these:

• Text messaging is the dominant communication tool of US teens
• Half of teens send 50+ SMS messages a day; "one in three send more than 100 texts a day, or more than 3,000 texts a month."
• Girls text more than boys

Many teens are going online with their phones (27%). This generally mirrors some of the figures for mobile Internet access in the broader population.

Many teens from lower income households or where there is no computer in the home use their mobile phones as a way to get on the Internet:

• 21% of teens who do not otherwise go online say they access the internet on their cell phone.
• 41% of teens from households earning less than $30,000 annually say they go online with their cell phone. Only 70% of teens in this income category have a computer in the home, compared with 92% of families from households that earn more.
• 44% of black teens and 35% of Hispanic teens use their cell phones to go online, compared with 21% of white teens.

Who pays the bill?

• 69% of teen cell phone users have a phone that is part of a contract covering all of their family’s cell phones.
• 18% of teen cell phone users are part of a prepaid or pay-as-you-go plan.
• 10% of teen cell phone users have their own individual contract.

According to the report, 26% of teens "live in households that do not have a land-line phone, and 29% of all families say they receive all or almost all of their calls on a cellular phone."

The implications of studies like this are fairly obvious:

• As these people come of age they will be oriented to mobile devices as central communication and Internet access tools
• Mobile will be their primary Internet access platform in many cases
• If you want to reach teens today, mobile is the most efficient medium and the one with the greatest potential reach 

There's considerably more to the report, which can be accessed here.