Fuck! Roald would fire me on the spot if he logged into my facebook! He'd see the collection of penis pics I put up everytime a member sends me one and get penis envy!
But seriously...this is going a little far on the part of the employers. I've even read accounts where colleges and high schools are making students 'friend' the school so the school can keep tabs on them.
I've read of a few accounts of people who got turned down because they weren't into social networking. It's becoming a damned if you do, damned if you don't type thing.
If you were stupid enough to use your real name on your facebook account (or any social networking), setting yourself to private or creating a fake profile isn't going to work thanks to google. Especially if you've had it for a long time. That shit gets into the search archives and stays there for a very long time until google recrawls the page. If it doesn't get enough traffic, it could potentially stay there for a very long time and there's jack crap you can do about it (ask the girls who get drunk, put their naked pics on their facebook and it ends up on forums like this with their real names).
So if you used your real name, try to hide your social networking account from a potential employer and their HR is savvy enough to find it, you'll be turned down for lying instead of simply telling them no.