Sounds sorta like the "Nintendo thumb" epidemic that was going around in the early 90's when kids were getting sore thumbs from playing so much Nintendo.
The iPod joins a growing list of hi-tech gadgets linked to possible health problems. Most recent is "Blackberry thumb", an RSI-like complaint linked to obsessive use of the portable e-mail and phone computer. There is also PlayStation thumb, said to afflict those who spend too much time on games consoles.