Doesn't matter where in the world you go, places where a lot of tourist come attracts scammers, thief’s and bad cabdrivers.
And every country and city is different, for example cabs are 3 times more expensive in Amsterdam than in Barcelona, in London are 4 times more pocket pickers than in Munich, in Italy there are a lot of scammers, much more then in Germany or The Netherlands.

My personal experience is that only the cab overcharges happens in every big city in the world.

The White Sneakers Myth is the most inaccurate. It isn't just fat old Yanks on vacation wearing them. It's mostly the locals and you can tell because they are usually cheap imitations of what we in the US buy from China and Japan. Velcro straps, giant brighly-colored platic/rubber springs in the heel, no designer logo and pointy toes are a giveaway. Blue jeans are everywhere but the dirty ones are usually non-Americans on vacation.

At Rome Termini we had three guys do the bump into you on all sides to my brother-in-law and he could feel them running there hands over his pockets. At the Venice train station we had a group of dirty looking kids ask us to help them look for their baby sister !!! We were a group of 11 people waiting on our train and had all our luggage stacked in a corner with about 4 of us guarding it at a time while the rest were off getting food. I am sure they were trying to lure us away so the rest of their group could swoop in and run off with our luggage. They were really keeping an eye on us but we were doing the same with them. It was quite obvious what they were up to.