there a few reasons a touchpad can go out, its difficult to narrow it down to one specific thing.
one reason could be applying pressure to the palmrest while typing. people who type more aggresively/faster apply more presure, the touchpad internals extended past the actual touchpad itself and under the palmrest, so when your pressing down on the plastics around the touchpad your flexing the board under the palmrest which can cause problems. This issue is more common when your a sattelite/remote user who doesnt use external perihperals or a docking station often, because you are taxing the system more. another reason your palmrest could malfunction is a problem with the pad itself, from what i understand, all the touchpad really does is detect pressure not actual motion above it, again this is user dependant, but ive noticed people who are more comfortable with the touchpad and the applications they use tend to apply more pressure than is neccesary because they generally use the "touch to click" function on the touchpad and while they are blowing thru their apps typing away and pounding down on the touchpad to click with their pointer, think about what thats doing the pressure detection components of the touchpad.
its not that they arent careful its just the nature of being an efficient typist. i do the same thing and i know how it works. when im typing on my portable I hammer the keys, i dont use the touchpad for that exact reason, its its precise peice of engineering and im not a precise user. i need an external mouse to function properly. when im on the road its nice because im usually just watching a movie or something, but when i do have to get down to the meat and potatoes paperwork im grinding away at the keys and moving that little cursor with the touchpad as fast as it will go so i can finish watching my movie, lol.
My mouse cursor intermittently wanders off on it's own. At this point the external mouse I use is inoperative and the only way to really control the cursor is the stick between G and H. The touchpad has some control but is not stable enough to control anything. I have a callous on my forefinger now from trying to use the stick!