Stories about terror plots should always be viewed with skepticism because virtually everyone involved has an incentive to exaggerate the threat. Let's look at the big players:
- The FBI agents and the FBI organization look more important and heroic if the threat is more severe and legitimate.
- The media gets to tell a more compelling story with a scarier threat, and may even succeed in terrifying their audience sufficiently to get them to check back tomorrow for more updates. And,
- The US government more generally gets political cover because hyping a foreign threat helps people rally around their government and worry less about some of the unpleasantries involved in addressing that threat. See, we really do need to spy on everyone and bomb hospitals in the Middle East; just look how many people out there are trying to kill you! And no, no one is explicitly making that argument right now, but you get the idea.
Adam Johnson, writing at Fairness and Accuracy in Reporting (FAIR), has a great write-up on how a story about an FBI sting operation in eastern Europe was transformed into headlines that ISIS is trying to go nuclear. Here's the link below: