suitcase nukes: fact or fiction?

USA Today : Government experts and intelligence officials say that the threat of suitcase nuclear bombs get vastly more attention than it deserves. These officials said a true suitcase nuke would be highly complex to produce, require significant upkeep and cost a small fortune.Counterproliferation authorities do not completely rule out the possibility that these portable devices once existed. But they do not think the threat remains."The suitcase nuke is an exciting topic that really lends itself to movies,” said Vahid Majidi, the assistant director of the FBI’s Weapons of Mass Destruction Directorate. “No one has been able to truly identify the existence of these devices.”