Lies are neither bad nor good. Like a fire they can either keep you warm or burn you to death, depending on how they're used.
Zombies have no memories of their former life. You wont see the undead trying to wash windows or do your taxes. All they know how to do is swarm and feed.
I think the general anxiety of the 1960s - '70s spawned our interest in the living dead. When people worry about the end of their world, they need a safe vessel for all their fears. Zombies provide that vessel because they're 'safe.'
That's the thing about zombies. They don't adapt and they don't think. Literally, you could have a zombie on one side of a chain link fence and you could be on the other side and they could be trying to get to you and six feet down could be an open door and they will not go through that door in the fence. That's why they're so scary.
Zombies are apocalyptic in nature. They belong to a class of monster that doesn't just hunt humans, but seeks to obliterate that entire human race.
Since 2001, people have been scared. There's been some really scary stuff that's been happening - 9/11, Iraq, Afghanistan, Katrina, anthrax letters, D.C. sniper, global warming, global financial meltdown, bird flu, swine flu, SARS. I think people really feel like the system's breaking down.