http://en.wikipedia.org/wiki/Sanisette
It used to be after they removed the old pissoirs it was hard to find a place to pee for free in Paris. There were pay toilets in or near the Metro stations. And if you went in a bar or restaurant to use the bathroom you were expected to buy something. I think they had pay toilets in the McDonalds.
Now there are free Sanisettes. They started out as pay toilets but now the city has made them all free.
But you may have to stand in line and wait as people can use them for up to 20 minutes. So the line outside backs up and some people give up and walk off.