Identity theft is still uncommon in Brazil. Also, people are used to filling out long forms because of our national bureaucratic mindset (it's not just the government, private enterprise is also very bureaucratic).
The result is that nobody blinks an eye at giving away _all_ their data. If you ask a complete stranger for his CPF (a number given by the Tax Service, a common Primary Key in many databases), they will give it to you.
We're lucky that most of our criminals just aren't very sophisticated (yet).
True. In many job interviews, people ask for your CPF (which is akin to a Social Security Number on the US, I guess) and even your parent's name. They probably check your (and your parents'?) criminal and debit history or shomething like that, but still, there goes all our data.