Personally I think one should not be too easily intimidated by them. They grow bolder bcoz pple pay up. I'm referring to cases where u r not intentionaly taking them, but they r in the pic, and they demand payment. I will ignore them. In D'jemaa el Fna, it happen easily bcoz the square is big, but do not be afraid.
I've posted a thread some time back, and there were some comments in it; u can take a look :