Let’s start with a basic concept that works all around the world: don’t be stupid! Use common sense. The only times I have ever had stuff happen to me in Buenos Aires is because I was being stupid and I gave a criminal an opportunity.
Every big city around the world, regardless has bad neighborhoods, pick pockets, and criminals who are waiting for opportunities. If you walk around texting on your iphone, wearing jewelry, at night, in La Boca (not a good neighborhood) then your chances of getting robbed are way way higher. If you are sitting at an outdoor cafe, with an ipad or laptop and your cell phone at your side and you are gabbing away in English via skype into your computer, you are making yourself a very obvious target.
I look like a foreigner, and despite speaking perfect Spanish with a near perfect accent, most portenos can tell within the first conversation with me that I am not from here. That means that I need to take extra precautions.
I was robbed in my apartment, while I was there, in early 2007. It was an extremely traumatic experience to see a stranger at the foot of my bed at 330am with my laptop. When he saw me wake up, he ran onto the balcony and basically jumped down the 20 or so feet that it was to get to the ground because by the time I got to the balcony he was gone.
But this robbery happened because I was careless with my windows on my balcony. We had left our sliding glass door open to let the air in on this 100+ degree day, and had fell asleep with it open. My wife, who is Argentine, had repeatedly told me that if we did that that we would be robbed.
But besides this one incident I can categorically say that I have not had one other single run in with thieves or criminals. But I can also tell you that this is because I take precautions to protect myself. Stay in groups. Don’t walk home alone at night. Don’t speak English super loud on the bus or subway, which is obviously a place where pick pockets can thrive. Lock your windows and doors. Keep your purses, wallets and backpacks strapped to your front, diagonal across you, or when sitting on the street, looped through the leg of a table or chair. Just don’t be stupid!