HappySqurriel on 06 July 2011
As a general rule, positive re-enforcement tends to work far better than negative re-enforcement and I think there are far better ways to encourage people to buy a new copy.
One thought off the top of my head is to create downloadable content for your game that is free for anyone who registers their game; and people who buy used copies would either be forced to pay for this content or possibly live without it. The difficulty with this approach is creating content that is worth enough to encourage people to buy your game but not seen as an essential part thereby forcing people to register their game.
