In the US it's usually just high amperage devices, motors, and 220 devices that are grounded, but I'm not sure the actual code on it.
The ground on a simple circuit like lights is just kind of redundant. Unless you were to wire it poorly in the first place it shouldn't ever have a purpose. It's just the point of human contact that really requires a ground, and if you stick your finger in a light socket the ground circuit won't help.