However, the shape of the keyboard, the size of the frame and other factors can influence how severely, if at all, you can be affected.

I, myself have recently developed a problem with the little finger of my right hand by using a certain brand of mouse when gaming which I thought felt great as I was using it--but after several months of use I discovered that I've torn a ligament in my pinkie finger by gripping the mouse too tightly as I moved it--and this is a big, stout mouse, not one of those tiny mobility mouses. The simple fact that finger became essential in the tight control of that mouse (incremental shifts for aiming the target pipper of a game) caused the problem and I've had to back off to a different, non-gaming trackball that puts no stress on the finger at all. Strangely for you perhaps, I use a trackpad for my everyday computing where the finger is almost never used--though I am a touch-typist using one of Apple's "chicklet" keyboards to type several thousand words a day with no pain or CPS.