For anyone who doubts that the texting revolution is upon us, consider this: The average 13- to 17-year-old sends and receives 3,339 texts a month—more than 100 per day, according to the Nielsen Co., the media research firm. Adults are catching up. People from ages 45 to 54 sent and received 323 texts a month in the second quarter of 2010, up 75% from a year ago, Nielsen says.

Behind the texting explosion is a fundamental shift in how we view our mobile devices. That they are phones is increasingly beside the point.

Part of what's driving the texting surge among adults is the popularity of social media. Sites like Twitter, with postings of no more than 140 characters, are creating and reinforcing the habit of communicating in micro-bursts. And these sites also are pumping up sheer volume. Many Twitter and Facebook devotees create settings that alert them, via text message, every time a tweet or message is earmarked for them. In October 2009, 400 million texts alerted social-media users to such new messages across AT&T's wireless network, says Mark Collins, AT&T senior vice president for data and voice products; by September 2010, the number had more than doubled to one billion. (Twitter reports more than two billion tweets are sent each month.)