The repetitive punching of keys on a miniature keyboard can lead to tendonitis in the thumb. The ailment is similar to "Nintendo thumb" which affects avid video gamers.
"Blackberry Thumb" comes from holding a PDA, or cell phone to text message, and repetitively punching the keys with your thumbs instead of your fingers. This puts thumbs at an awkward position and can lead to pain, redness and swelling.
There is a solution: cut down on writing long emails on little keyboards, or hold the device with one hand and dial with your fingers on the other hand.