What are shadow profiles on Facebook?

As Zuckerberg arrived at Capitol Hill, he looked grim as death. Increasingly uncomfortable questions have been asked of Facebook. How much information does Facebook collect about its users? How much of that is violation of an individual’s privacy? And how safe is all that data in the hands of Facebook? In fact, it is astonishing that he had not envisaged that a day would come when his company’s gigantic appetite for gathering data and using it for profit would not face a backlash