Marrakech is a great place. People in the souks and the central square usually fall into two groups - those who get photographed for a living (eg water sellers) and those who don't want to have their pictures taken. As regards the second group, I don't really blame them. I don't want mine taken either. But then, it might be a good idea to get a good guide for the day who is able to approach those people you really want to take photos of. If we're talking elderly men (okay, women are out because of religion), you really have to bear in mind that they may only speak Arabic and/or French. Approaching them in their own language is 100 times easier than having a foreigner waffling in some crazy tongue brandishing a camera at the same time. Also, it might help to go there one day, talk to them, and then come back a day later with a camera.