Not just Paris, you should see the state of the otherwise lovely Bordeaux! Maybe I'm just missing something, but I have to say I rarely notice dog mess on the streets, and think that most owners are being responsible. I remember as a kid walking down Felbrig Road to school in the morning, and there was loads of the stuff! Don't see that at all now, in fact, maybe it's because it's actually quite rare that people notice it if there is a random turd steaming on the pavement. With regards the green, I don't really have a preference either way, although a fence does stop kids running off which has to be a good thing.