@ Gnac
Here's a link that shows how exactly the stick works: http://electronics.howstuffworks.com/n643.htm (You need to scroll down a bit.)
While he incorrectly labels it as analog, you can clearly see it works on digital principles. The varying amount of light to the photocell determines the amount of current, which in turn allows the controller/system to know where the joystick is positioned. When the light is blocked there is no change in current, and no change in the sensing of the joystick position. In other words, the controller operates only on a set number of variations/currents, with "dead spots" in between them. While I'm sure these "dead spots" were very small, it still didn't allow as much accuracy as a potentiometer based stick.
@ Nick
Thumbsticks have existed before the N64, as the Atari 5200 and Vectrex featured analog sticks that could be manipulated with just your thumb. And, since Sony had started working with potentiometer based joysticks back in early 1995, they may have eventually put out the Dual Analog, anyway. However, there is no evidence to prove or disprove this, so you may very well be correct, as the N64 controller was the first to have a thumbstick during that gen of consoles. So it may have inspired Sony to develop the Dual Analog, while using the more accurate potentiometer tech.
Your last point is very true, and really was my point to begin with. All companies take existing tech and improve upon it. So to bash one company for "copying", while making excuses when another does the same thing, is quite hypocritical. Really, there isn't much gaming tech of late that doesn't find it origins, in one form or another, in the early to mid-80's. This even includes motion controls.
