I know this has been brought up in a few discussions I've seen- employers regularly snooping on people's facebook info and prohibiting people from complaining about their jobs or co-workers. I honestly call foul at that level- freedom of speech means people have a right to complain about their jobs or their coworkers as long as they are not doing so at the company's expense or on the company's scheduled time.
This? I would honestly refuse to provide it, and if they refused the application on that basis I would contact a lawyer to represent me in a legal suit of cyberdiscrimination against them for it. They have no right to intervene in my personal affairs, and the management that thinks they do should be fired.
Besides, the only facebook account I have is for my own company. If they really wanted to see how little was in it, they would first have to sign a nondisclosure agreement under my company's name in order for me to give them permission to access any of that information.