It would appear that I am still a rude wee shite in the land of France. After the incident in the Tabac I've gotten into the habit of calling everyone vous, just to be extra polite since I'm always forgetting to kiss them. However, its now dawned on me that calling someone you know well vous might be just as rude as calling someone you don't tu. I can't be sure but I think its like walking up to your best mate and saying in all seriousness "who the fuck are you?". Or "Goodness, you are really OLD."
(The reason I can't be sure is that French people, unsurprisingly, talk to me in French. To which I smile or laugh or frown and hope its the right response.)