I've not noticed a significant worsening of the security situation, although I have heard some Argentines (well-to-do sorts who have very nice flats in Puerto Madero and have offices in Microcentro) commenting about crime in the center recently (robbery in front of a respectable hotel at knifepoint and the like).

These same say that the neighborhood I live in (Palermo Hollywood/Chacarita) is very dangerous. I don't see that, and I walk most places, take the colectivo from time to time, taxis... but I take care to keep my iPhone in my pockets and out of sight when crossing the tracks between SoHo and Hollywood, and certainly wouldn't choose that as a place to count the money in my wallet!

I tend to think some street smarts can probably avoid 95% of the risk, and the other 5% is about as random as things like identity theft and credit card fraud. Things happen everywhere. What tends to happen where is the variable.