Well, why not?
Glenn Reynolds suggests, somewhat tongue-in-cheek, that a "fireball [which] fell from the sky and slammed into southern Peru over the weekend, creating a huge crater that emitted a sickeningly smelly gas" may precipitate an attack of zombies. Anyone who is seriously worried about repelling an onslaught of zombies should visit Zombie Defense Training, a site which contains useful tips which may one day save your life. One handy reference you will definitely want to own is the Zombie Survival Guide, published by Random House. This is serious stuff folks.
I have often thought that a really enterprising screenplay or thriller writer might strike gold writing Zombies Versus al-Qaeda. There are two possible plotlines. The first opens when zombies are about to begin an attack on an unsuspecting town when suddenly they become aware of another threat ... can zombies remember they were once men? The second reverses the scenario. The baddest group of terrorists on the planet is preparing to slaughter the student population of an entire high school when suddenly an attack from the Undead forces the hardened al-Qaeda to consider whether they should join forces with humanity to repel these creatures from beyond the grave ... Sample dialogue: "We're not afraid to die!" "We're already dead!" "I became a zombie on 9/11." "Quick Abdul, the suicide belt. Do you think an IED will stop them?"