Crime is apart of life no matter what city you are in around the world. You could be in New York City, Washington, D.C, or even Des Moines, Iowa and get robbed by somebody on the street. While traveling through South America (Buenos Aires in particular) you will start to hear stories of people getting cameras, money, or even Ipod's stolen while walking down a street.
I traveled through South America for almost 6 months, and I lived in Buenos Aires for almost 2 months. I had no problems with people trying to rob me, nor did I have anything stolen from me during this time period! Again, I had zero problems. So do not listen to people who say South America is too dangerous to travel through, because if you are a smart traveler you will avoid shady situations. During my trip I was careful about not flashing money in the streets, I would take pictures and then put my camera back in my backpack, and I didn't wear any jewelery.