What % of teens use email on a daily basis?
I don’t have anything but personal experience to back this up, but my understanding is that teens who use Facebook on a daily basis also use email on a daily basis. That is to say I think the conditional rate is 99%+. If you’d like to draw any general conclusions about teens, consider that while Facebook may get increasingly more face-time with teens, they don’t related to other media as a burden. Phone calls, sms, Facebook, email, etc. are all communication tools that happily lay dormant until the moment they are needed. Email is more popular than ever right now, but that is true for almost everything else.
