Spend some time browsing the Wiring & Shielding section of the >GuitarNuts< website.

Briefly, any time you have more than one ground path, you have the potential to pick up noise. When the case of a pot is used as a convenient place to solder ground connections, and then the pot cases are linked together, you end up with ground loops (multiple paths). This is made worse by some builders who put a piece of foil on the control mounting surface of the cavity.

Done properly, the entire guitar should have only one ground point: the shell of the jack. In the "Quieting The Beast" article at GuitarNuts, he shows a slick way to add anti-shock protection by capacitively coupling this single ground point. I've used these techniques for years. They not only significantly reduce noise, but they can save your life!