I don't know for sure if this is a scam or not but I'm suspicious because I received an email inquiry to my For Sale add on Craigslist which implied that the sender was interested in buying my truck. I replied with phone # and address info and the sender replied by asking if I had a DiscountVin.com report on the truck, and then went on to tell me how great DiscountVin is, how it's less expensive than CarFax, blah, blah, blah.
I almost fell for it but before I ordered the DiscountVin report I searched for reviews and found that others had had exactly the same experience. Viewed in that light all the 5 Star reviews sound like they came from shills.