I'm wary of flaming but... fog lights are a nuisance. It is almost never so foggy that normal headlights are inadequate. People in the UK have started using front fogs all the time, like I'm going to mistake their 316i coming up behind me for a Le Mans GTR emerging from the pits. It's just rude: you wouldn't drive around with your main beam permanently on. And they are totally useless, even in fog!
As for rear fogs, they are down right dangerous in all but the most extreme situations. Like any over bright light, they are a serious distraction for following drivers. And they make brake lights a lot more difficult to perceive in an instant. That is the reason why there is only one fog light on German cars. I guess the logic of those who use rear fogs at night or in the rain is that it makes them more visible. In fact it makes them less visible when it counts: when they are braking. When it is dark and wet, with water on the screen &c, they make it very difficult to see for following drivers.
People also forget to turn them off. At least the MB light switch makes this stupidity impossible. The UK police occasionally have a purge on this sort of thing; should be a hanging offence.