Hirsch, who said he has seen at least a couple of patients with injuries related to their PDA or thumb keyboard, said he tells patients to send short answers on the devices. "Many people who are traveling use their BlackBerry to save them time," he said. "Thumbs were not designed for individuals to do this without certain limits.
Another problem I've wondered about for a few years is whether there has been (or will be) an increase in trigger finger, arthritis of the hand, or similar cumulative trauma disorders along with the increased popularity (near ubiquity) of computer mice with scrolling wheels. After even just 10 or 15 minutes of intermittent scrolling while reading online articles, for example, the joint at my finger tip (the distal interphalangeal (DIP) joint, to be exact) becomes sore. After a few hours, I start to notice pain at the base of my index finger.
The Harvard Vision Sciences Laboratory, however, recommends using the scroll wheel more (see tip #4), I assume because it eliminates the wrist-flicking motion of moving the mouse up and down the vertical scroll bar on the right side of most Windows and Macintosh applications. I don't really agree with them on that point. I do like tip #5, though--it suggests using keyboard shortcuts to eliminate mouse movements.
UPDATE: For comments, see the original blog post here.