I just talked to a fellow that did a CARFAX report on his RT before buying it... clean. After he had the car for several months, he started to feel something was not right. He then spent a lot of time chasing the title history.... turns out the car was a repaired car, title was supposed to be stamped in TN, but it wasn't. Original buyer knew car was a repair, but said nothing to the next buyer, a broker, who sold it again, this fellow drove it a bit (without registering it) and then traded it to a broker, who then sold it to another broker, who made the first broker buy it back, then the broker sold it again to the person who took the time to run the CARFAX report to make sure he was not buying a damaged car.
Bottom line, carfax will pay him 10% of the wholesale on the car, which is not even going to cover his legel bill.
He will likely lose 10K on this car before it is all said and done, a dream turned into a nightmare.
Carfax is a good start, and it may turn up some good things, but the best insurance? Have an experienced certified Viper Tech put the car up on a rack before buying..... just look at the wrecked Viper thread to see why.