The Thumb Generation
The New York Times > Technology > Circuits > All Thumbs, Without the Stigma: "So important has the thumb become on gadgets in Japan, where text messaging caught on earlier, that a certain demographic group is referred to as oyayubi sedai, 'the thumb generation.' Dr. Tenner pointed to findings that young Japanese, accustomed to using their thumbs to send messages, are now using them to do other tasks - like pointing and ringing door bells - traditionally the realm of the index finger."

"Of course, there is some worry, even among users, that speed typing with one thumb could create repetitive strain injuries, like joystick wrist. But the early evidence is inconclusive, according to people who follow the field. ... Professor Katz said the thumb was unlikely to face as many problems as, for instance, the wrist. The reason, he said, is that the wrists have lots of tendons and have not adapted well to the unexpected use of the forearm for typing."