Nvidia should partner with Steam. Steam has enough meta-data on user accounts to be able to offer a level of certainty about how accurate and authentic a given account and it's user information is. You could then use a trusted enough Steam account as a one-per-customer method to sell a card to.

You wouldn't have to monkey around with hardware freedom and even if a person decides to re-sell it at least it had the chance of being used by a "real gamer" first.