Social Security Numbering System Vulnerable to Fraud, Researchers Say

Yes, I try to imagine that my SSN has already been spread all around the Internet, and thus remind myself that I can't consider it secure.

The biggest risk is identity theft where the culprit uses your SSN to gain credit in your name to buy stuff. You can protect yourself by placing a "freeze" on your credit report. This is essentially what LifeLock does (simplified). But you can do it for free by calling the rating agencies yourself:

http://www.ehow.com/how_4447446_block-companies-checking-cre...

In America, knowing someone's SSN, date of birth, address, and a few other pieces of information (mother's maiden name?) are enough to get credit in their name, break into their bank accounts, and perform other forms of malfeasance. It's a really bad system.