Below is from Snopes.com Full story LicencePlates So, if your licence plate is stolen it's probably NOT going to be for gas usage. Here in Kentucky, we only use 1 plate (in rear) so it would be really dumb of someone to use a stolen plate. A person is going to notice if it's missing way faster than car that requires 2 plates.

Therefore, while the warning being spread in e-mail is valid, it is not one that needs be spread to one's nearest and dearest at the speed of light. The ill-intentioned do make off with license plates, but it is much more likely purloined tags will be used to disguise stolen vehicles being moved from one location to another or armed robbery getaway cars than they will to obscure the identities of those filching gas. If not to protect yourself from accusations of gas theft, if you discover one of your tags has gone missing, you should certainly notify police, because by so doing you might be helping to foil a far more serious crime in progress.