True, but if the rear lights suddenly stopped working then you'd expect the manufacturer to replace those under warranty regardless of what you did to the engin

True, but if the rear lights suddenly stopped working then you'd expect the manufacturer to replace those under warranty regardless of what you did to the engine, wouldn't you? Note that I'm not necessarily saying Apple have done anything wrong in this particular case, but making any modification (a sticker on the back?) shouldn't automatically void any warranty claim on the whole device. IMO.