Definitely agree with the OP -- Rio...and Salvador & Sao Paulo are dangerous cities. They are incredible cities -- but you do have to weigh the risk that something like this could happen to you. OP -- I'm glad you're OK, and I'm sorry you had to go through that. I've never had any negative experiences (I speak Portuguese/am usually with locals) -- but all the locals I know have been robbed at least once in their lives.

While I don't have specific statistics -- I believe in 99% of cases tourists are involved in muggings, so you'll end up out of some cash and a cell phone, but they are terrifying nonetheless. The recommendation from my Brazilian friends is to not carry things of value with you if you're going someplace risky (which anywhere on/near the beach at night, unfortunately, I would consider risky) -- but have enough cash to satisfy a thief (50-100 reais).

I never carry anything aside from cash, one credit card/atm, and a photocopy of my passport with me in Brazil.

It is, however, still one of my favorite places in the world -- and I'll be back in November.