If driving in Europe with greater than 50 metres visibility with a rear fog light on, the driver would get a head spinning fine if spotted by police.
My former Peugeot 405 and Mercedes both had/have rear fog lights but they were/are used properly.
The number of numb-nuts drivers here with Volvos, BMWs, Mercedes and Audis (mostly Audis and Volvos though) that have them on all the time is mind-blowing. It is just another reminder about how poor driving standards are on this continent, just like the lack of lane discipline, which makes high speed limits impossible in North America. Rant over.