Warning About Magnetic Switches

I've always unplugged machinery before working on the motor or changing the blade. It seemed a bit overzealous, but machinery can remove fingers and more. You know: "It slices, it dices, it julienne fries." This is not what you want done to parts of your body.

Today a friend sent me a link that suggests there is more to unplugging your machines before working on them than just paranoia. I could not corroborate this information elsewhere on the Web, but the article describes how machines with magnetic switches can be tripped just by being bumped or otherwise shaken adequately. It makes sense. You can bet I'll be extra careful to unplug before changing blades. And I'll be looking for other sources that describe this phenomenon.