"Facebook is discriminating against people based upon who they are and where they live," Housing and Urban Development Secretary Ben Carson said in a statement. ( Carlos Osorio/AP)

The Department of Housing and Urban Development (HUD) is suing Facebook for allegedly violating the Fair Housing Act. HUD says Facebook does so by allowing real estate companies that buy Facebook ads to choose which groups of people see their ads – enabling advertisers to hide ads from individuals based on race, religion, familial status, disability and other characteristics. Either Facebook or HUD can move to have the case heard in federal court, which could result in an injunction or civil penalties.