Can you be denied a job because you are not on Facebook?

How important is a Facebook and linked in to employers?  Someone recently told me they were removed from a job candidate list because the employer could not find their Facebook or Linked in profile. This person does not have a profile and is not into social media. The employer told them that they were not on the internet grid so it was difficult to know about them. Is that even legal? In addition to a background check it seems Facebook has become the place for an employee “psychology” check. Here is a question – After seeing what some of your friends post on Facebook would you employee them?