It's very much like reality TV advertising, build a set and then let the public vote/express their views which gives the dealer ratings. All well and good but you're letting people vote on things they may not fully understand. Rory experienced a bad review because the customer felt wasn't happy about a px value, I can see more of this happening in the 'Car Guru' model, people venting because they don't get their own way basically.
The way he talks about the 'condition' of cars shows a complete lack of understanding too, a basic HPI type check doesn't make the car good condition, it may not have finance or be a CAT C but it could have poor paint on each panel, smell of dog and fags. He talks about dealer pricing to get a 'fair deal' marker but surely that undermines the very concept of a review type site, the word 'Great' is stronger then 'Fair'. Who wants to take someone out for a 'fair' meal when for the same money it can be a 'great' meal.
It's yet another case of a company getting data and trying to sell it back somebody, be it a dealer or customer in a different way. The problem is the data it corrupt because a car is about how it looks and drives which data can't tell you. It also discounts many maintenance issues such as DSG or Haldex oil changes, type of tyre fitted etc so in a way it restricts the quality of the product the customer end up with.