People who think they can "hide" their personal info on facebook need to remember that expression about having a fox guard the hen house. Thinking you are anonymous or private on facebook is one of the stupidest assumptions you could ever make.
BTW, is facebook REALLY so addictive to some people that they need more than one account? Get a life!
For years, they preached about not giving out RL info on the web. You could be stalked, ID theft, and all that crap. But NOW cause of facebook, people foolishly post EVERYTHING from their birth date, phone number, what they had for breakfast, where they are every moment...
But that is OK, go ahead and hide your deep personal life on facebook, no one will find out since their security settings are so good.