A look at the evolution of a terrorist-attack warning: one part truth, one part rumor and one part fear

Imagine getting a call from your doctor one fine afternoon and being told that you are going to get cancer. You seek a second opinion, only to be told that you probably won't get cancer after all; it's just that the first doctor wanted to hedge his bets in case you ever got sick and sued for malpractice. Just as you are absorbing that dark bit of news, a third doctor breezes in to assure you once again that you're safe from cancer--but you will contract a fatal illness of some kind at some point soon. Before long, you'd be sitting...