Thought I would find a legitimate answer to duping in here, boy was I wrong. Same self professing nonsense about it being cheating because of breaking PSN rules? The PSN rules do not cover duping, because to dupe all you do is gift a paint to anyone including yourself and copy your original save back to the main game and gift it back.
A cheat implies gaining an unfair advantage that would somehow make it to your benefit to do it. Getting multiple paints colors gives you an advantage of, being able to paint more cars a particular color...

The only grey area I see is that if you weren't able to copy your file save then you couldn't dupe but even that wouldn't stop you as you could just make multiple PSN and game saves and just send all paints you acquire from the dummy accounts to your main account. Since they give you free paints everyday now, that's even easier than duping, more random and less controlled but still getting paint you didn't do anything to "earn".
Same thing for duping cars, I don't see how this gives anyone an unfair advantage at all. If you sucked at driving a level 0 car you won't all of a sudden get better if someone gifted you a level 23 car. I'm not sure where all this elitist crap came from in GT, but it seriously needs to go. Face it PD screwed up with a great many things in GT5. The paint shop is the worst offense as Kaz and Co. thinks that everything needs to be some sort of mini game to be interesting...no it's stupid and ignorant especially considering the amount of cars and the fact you can't preview what the paint would look like on your car

. These guys seem to like to make simple things complicated for no apparent reason. I actually thought that after I got the 256 color trophy, that the paint shop would be unlocked and I can use paint chips as often as I wanted...yea why would something so simple in implementation go so wrong?
The non repeatable prize car gifts, that is just as bad, it's like they want to force you to go trade cars...but there is no car trading system like in Forza...so I find it a stupid idea. Coupled with the fact that over time and usage of the car it's performance becomes irreversibly lower forcing you to buy a new car. Prize winnings are dearth and selling cars you own nets you very little cash, these compounded reasons alone is enough to suck the fun out of playing the game. So people figure out you can duplicate cars and thus the issues were overlooked for their shortcomings. Now that the restrictions are back, what do you think is going to happen? People will find different ways to get the most fun out of it. Not every idea out of PD makes much sense in the spirit of gaming fun, why fix what wasn't broken in the first place? GT4 prize system was just right, who cares if people had multiples of the same car, big deal. You sold your old worn down car and started using the back up and if you needed another back because you loved that car, you just went and won it again. Simple fun.
GT5 not so simple and what's worse is that now that UCD seems to be on a constantly changing car rotation now. I'm sorry but I have a very advanced piece of tech in the PS3 and you're limiting me to just the colors of all the cars in the game? Why? This thing has the ability to display 16.8 million colors and I am stuck with less than 1000 paint colors? Of course I'll dupe paints why not, I'm already limited by color choices and inability to actually paint the car to whatever design I can think of. People we want fun out of our game, not a slough fest with some archaic paint scheme. If we keep bothering them, perhaps PD will just give us a paint shop that has all the real manufacturer paint colors and a color sampler that allows us to make any paint we can. Simple things that lend to identity, come on PD.
They want each person to have his own identity online, but you have a crap load of limitations which there is no way around. All cars that can be painted can only use the paint that everyone else will at one time or another...get it together PD. Play FM3 and see what a paint shop is all about and what it can do for boosting interaction between players aside from just racing...oh and where is our tune saving feature? What's the point of a lounge and track day, when you can't save multiple set ups for one car...I'm not resorting to writing that stuff down. Get it together PD. I love playing this game but glaring issues that shouldn't have been there in the first place is sapping some of my enjoyment out.