They do it late at night when their parents are asleep. They do it in restaurants and while crossing busy streets. They do it in the classroom with their hands behind their back. They do it so much their thumbs hurt.
Spurred by the unlimited texting plans offered by carriers like AT&T Mobility and Verizon Wireless, American teenagers sent and received an average of 2,272 text messages per month in the fourth quarter of 2008, according to the Nielsen Company -- almost 80 messages a day, more than double the average of a year earlier.