ALESSANDRO ACQUISTI gave a cool talk at the 2011 BlackHat presenting his research findings which indicate that by taking a picture of your face, that picture can be correlated with your facebook profile, which can be used to take simply your birthday, and using that information, using a computer to guess your social security number with significant accuracy compared to random. here is video
<a href="http://www.youtube.com/watch?v=fZQ7Th9L5ss" rel="nofollow">http://www.youtube.com/watch?v=fZQ7Th9L5ss</a>
People can only escalate the cost of having their identities uncovered. I don't believe it's possible to be completely anonymous. Of course, when the people who want to know about you have no economic limitations (i.e. governments or the odd billionaire), you will eventually be found out.
Another great reason to protect your online identity. I don't use any of my real information on any of the social media sites I use simply for this reason.<p>Had these people taken better steps to conceal their identities, they wouldn't be in the jam they are now. Live and learn I guess.