[uses]

You definitely don't want actual counterfeits to exist in the game at all. Even if they're for personal use, they'll end up getting into the supply, and someone gets screwed over because they don't know any better. Instead we use "proxies" which aren't meant to be passed off as the real thing, but represent it in-game. They usually have a different art, or a different card back, or some other obvious difference from the real deal.

[tsimionescu]

That would still be irrelevant for the game, it would only be relevant for the traders. The game would still work exactly the same if the model were that you would go to WotC with a specified deck, and they would print it for you, at a standard cost per card, or even if they cost more for more powerful cards. It would kill the trading, of course, but that's entirely unrelated to the actual MtG game.