When I bought one of my listed 916's I was very pleased with the result. When I looked back at the original ad I noticed certain strange discrepancies. The seller, (previously a poster on this site) had used photos taken at least three years before the car was advertised. The seller used photos showing a personal registration and because of his meticulous keeping of car history I found a folder of the old tax discs to show that the car had been put back on the original number for quite some while.
Luckily the car has been great with no problems but this does show that the photos you see in an ad may not represent a current timeline.
Some might say that to use a three year old photo to sell a car is 'borderline' dishonest, luckily in my case I got the car that I wanted but some might not be so lucky so don't just assume.