I remember on my highschool's Europe Trip there was 30 people from my school (East Coast Canada) and about 30-40 from a couple schools from different parts of the US. So we mingled with the US kids, and one of my friends became smitten with one of the girls so they hung around for most of the trip. So on the forth day of our trip and we're in some square in Rome (I can't remember the name, small oval-ish shaped square with a large-ish fountain with carvings, beautiful place, but filled with scammers - it wasn't the Trevi).
So as we're leaving this area we became a little dispersed and my friend and the girl from the US are the last ones in the line and get cut off by partners of the scammers (didn't know at the time, but was obvious looking back). A small group of people essentially just walked across the front of them to make them slow down and stop to segregate them from us. So we had no idea and we're all walking into an alleyway with the tour guy when I hear a few of our names being called. Look back and here is our friend and the girl being harassed. A few of us shouted at the tour guide and teachers and then ran back down to the friend where the scammer had tied a bracelt to each of their wrists within seconds and was demanding money.
Then the scammer looked around and here is 30 people surrounding him and when he demands money from my friend and the girl we all just started to circle him and give him hell (nothing physical, just intimidation game). He realized that he had no chance and I even noticed a few of his buddies had backed off and essentially was going to let us do whatever we wanted to him.
One of the guys from my school was on the provincial rugby team and was scarily huge (6'5. 250+lbs of pure muscle) and decided to get right up close to the scammer and towered over him. The scammer cowered and pleaded saying something in Italian we didn't understand and then booked it, pushing his way through our group that surrounded him and ran off in the opposite direction we were heading. Needless to say he probably went right back to it when we left. But I think it made him think to be aware of just how large some groups are.
Honestly, I really enjoyed myself, we mingled with the gypsy's and the harmless photo scammers giving them some change we had (like €0.10 at most) and had a great time. I will say this though, do not get a photo of yourself giving your friend a high five in front of the Acropolis..