I would find very strange if you were hassled in Paris for taking pictures. Just keep normal behaviour. Generally speaking I do take pictures of people, and also in Paris (more so, to take pictures of cafe life and such) just don't go into the nose of people.

I was actually the subject of a "cafe life" stock picture. I was with a friend, drinking a beer at one of those small outside tables with three legs (guéridons) boulevard Saint-Germain-des-Prés (you pronounce that with a close e in Prés and an open e in Germain, avoid sounding the final "t" and all should be fine ) almost in front of Danton monument if I remember well and a she-photographer with a serious "but digital" camera came in front of us, took a picture blatantly of the two of us, and went away without a smile. I had no problem with people taking advantage of my discreet and elegant beauty in any case*

I had four nocturne tripod sessions:
Montmartre;
Opéra - place Vendôme;
Notre-Dame - Hôtel de Ville;
Tour Eiffel from Champs-de-Mars.
Never had anybody interested in what I was doing.

The only place I found where they tell you not to take pictures is inside the Sacré-Coeur, which is a place where you would need in any case a tripod or a stand of some sort. That's a stronghold of bigotry so no surprise they have some added paranoia added to top it off.

Fabrizio

PS *Her caption probably was: couple of photographers destroyed by a tour of Paris in a sunny day under the delusion a beer can put them in shape again.