Unlimited texting is hella cheaper than unlimited minutes.
I'd venture a guess that many of the texters came from this environment. I don't mind texting for a quick comment or question when you don't want to bother someone with a phone call, but if we're texting back and forth for more than 5 minutes, it's time to pick up that phone and dial 'cause my time's a-wasting.
These kids are FAST! I swear, my teens can respond to me just as I'm pressing "send".