I can only type on my Blackberry for a few minutes before my thumbs start aching. I can't imagine how painful it would be to type out a 2- or 3-page document on it, which is why I cringed when I read this story over on TechCrunch. As they confirm in the comments, it's not that half the books read in Japan are on a mobile phone...half of the bestsellers are actually written on one!
Sounds like it's time to invest in medical supply companies that make splints other devices like the one shown with this post... Ouch. Seriously, I feel the RSI of typing for 30+ years with ten fingers. Can you imagine what that would feel like if all that output came from two thumbs?!