I am not an attorney or hold a law degree, but I have been interested in this kind of thing and I do know the following as fact:
1. During the course of 2010, auction companies have dropped cars from auction lists because sellers making claims about the car (ownership, equipment, etc) could not support their claims with the proper documentation (bills of sale, copies of titles, factory correspondence, numbers on cars, etc).
2. There are at least two lawsuits pending because the buyer purchased the car in significant measure based on claims made by the seller, only to find out the seller mis-represented the vehicle (note I did not say lie). The judges were asked to drop the suits because of Caveat Emptor (let the buyer beware) claiming that it was up to the buyer to verify claims made before purchase. The judges ruled that if a claim about something is made by a seller the seller must either indicate they cannot support the claim with fact, or provide the proper proof. In other words, the suits are still pending and the judge felt there was merit to the case.
3. The old car hobby has existed long enough so that cars have changed hands more than once on a claim of "the person I got it from said so" regarding car history and condition. No documentation, just say-so.