Unfortunately for you, businesses have many ways to view your account - so I suggest that you just change your name for a short period until after you obtain the job haha. Then cover your ass and be smart about your facebook usage in conjunction with work activities. It's extremely easy to get sued for information exchanged on facebook these days. Also keep in mind that although you may have made your account private, once you published something on facebook, that information is no longer private and you can never stop someone from using it in ways it was not intended.
* fun fact for you, it's being discussed in the US whether or not corporations can fire you if you deny them access to your facebook accounts. Something to mull over!
**edit: They can add your friends and get onto your account that way, no matter what your settings are!