Vin's have been around since Day One. Titles, on the other hand, have not. In certain states (Alabama and Georgia come to mind!), titles are not necessary on vehicles beyond a certain age (I think 20 years). BEWARE the so-called "title services" operating out of Alabama and other places. Mind you, this relates in part to the VIN tag issue, but important, nonetheless...
There have been raids on places like Boyd Coddington's Rodd Shop is SoCal concerning alleged "fake" numbers being used on new street rods, etc, amongst other things. Boyd's shop was raided the first week in October by 24 cops from several state agencies, all yielding riot gear and armed to the teeth! See the latest Street Rodder Magazine for all the details. Other people in California are in a great deal of legal trouble for using these "title services", the one mentioned specifically in the article was Titles Unlimited in AL. California is essentially trying to make all of these rods, especially the fibreglass cars, register as NEW cars and not as the year they represent. I'm combining two topics here, but the result is the same...
First, take a pass on ANYTHING without a title, unless that state doesn't require one. Second, if the numbers are gone, pass. Third, ALWAYS get a bill of sale!!! That kept my butt from going to jail one time when the '63 Chevy truck I sold to a guy wound up four months later involved in a robbery after the sale. The cops came to my door one day, asked me about the truck, and I produced my copy of the BOS. Because of that, I proved I no longer owned the truck, and it had the guys' name and address on it!!! They caught him about an hour later. He never registered it in his name (Oklahoma plates stay with the vehicle, NOT the owner (I hate that!)). OK law gives you 30 days to transfer title, but sometimes people will run the vehicle until the tag expires and then title and tag it, even though the title has your notarized signature on it as the seller.
Common sense applies, above all.