This comScore chart which shows the massive gap between teens and all other ages as teens have rapidly started to rely other communication methods instead.
I witnessed this firsthand over Christmas as I watched my 14-year-old cousin play with all of her tech toys: iPod Touch, PSP, and mobile phone. She had just received the iPod Touch as a Christmas gift and was loading it up with apps while texting her friends with her mobile in the other hand.
There were two things that I noticed while observing her through this process that directly relate to this study. First, she showed little interest in setting getting email on her iPod Touch even after I showed her where she could set it up and how email looks on my phone. Secondly, while she was adding apps, some of them required signing up for an account in order to use the app. This meant accessing email to confirm her address, and it was the only time that I witnessed her using email at all.
Here are two other studies that provide a better picture of exactly how teens are choosing to communicate without email: