I have read through all posts and have not seen this argument raised yet in terms of who this glitch actually effects, so I think it might have some merit. First let me say duping cars for your benefit in single player I have no problem with, but when it comes to online racing I have a huge problem with it, let me explain.
I mostly race nascar races online. As we all know when racing online your car will slowly lose horsepower the more laps you put down(Oil, and engine degrading) and I feel I was forced to purchase every nascar in the game because people have duped so many nascars in their own garage that they now have 30-40 and can run a fresh car every race. They do not need to change oil, rebuild motors, or restore the chasis. Every race it's a new duped car that has max horsepower. Is this fair? Honestly I don't think it is. Now clearly I could go buy 30-40 nascars and do the same thing, but that's not what these people have done. I know they are using duped cars because for some reason all the "dupers" really seem to like to talk about how many duped cars they have.
I really don't care what people are doing in the single player portion of the game because as has been stated it effects nobody, but when guys are getting online with 30 duped cars all of the same type so that they can always have a fresh car car then it's effecting me and every other racer in the room. If you think this is a minor gripe then go do some online nascar races and see how much of a difference it makes when you are running a car that has been more than broken in running at 850hp versus a fresh car with 892 hp. It will change your lap times at Daytone by 1.5 seconds.
I know most "dupers" will have some argument for this, and it will somehow be my fault, but in my eyes this is cheating. It's using a glitch/loophole to have an advantage against other racers online. I'm suprised I have not seen this mentioned yet because I think it's the best case of this glitch effecting other online racers. I'm sure it happens in other race rooms as well and not just nascar.