Here's the email I got. I checked out as true on Snopes.com
"CAR THIEVES
Just heard this from a friend. Apparently car thieves have yet again found a way around the system and steal your car or truck without any effort at all.
The car thieves peer through the windshield of your car or truck, write down the VIN number from the label on the dash, go into the local dealership for that car brand and request a duplicate key for it from the VIN number.
Car dealerships make up a duplicate key from the VIN number, collect payment from the 'customer' who's really a would-be car thief for making up the duplicate key -- the car thief goes back to your vehicle, inserts the key they've just gotten and off they drive with your car or truck.
They don't have to break in, don't have to damage the vehicle and draw no attention to themselves as all they have to do is to walk up to your car, insert the key and off they go to their chop shop with your vehicle!!!
Can you believe it?
To avoid this from happening to you, simply put opaque tape (like a strip of electrical tape, duct tape or medical tape) across the VIN label located on the dash board. You can't remove the VIN number legally under most state laws, so cover it so that it can't be viewed through the windshield by a car thief.
Anyway, feel free to forward this on before some other car thief steals another car or truck like this."
Here's the link on Snopes that verifies it:
Snopes' story on covering VIN number