And on the subject of lightbulbs. The Edison Screw is very dodgy because the coarse threaded outer contact is connected (should be) to neutral. If it is wrongly connected then it can be live and easily touched when being screwed in. You cannot rely on the switch being off. Many light fittings are very badly specified and, despite being just as potentially lethal, they are supplied with bare wires and the regs for house wiring seem to change from needing or not needed an earth conductor. You just can't buy other domestic appliances without plugs these days (moulded, usually) but home lighting circuitry is just a mess (at least in the UK).