Duping is making a copy of an item. That's it. But it's the damage it can cause to the online aspect of PSO. More and more games are being passworded online by legit players who don't want dupes in their game because they "spoil" the economy of the game. As more and more games become locked, the less chance you have of meeting nice people.
I doubt very much the GC will ever get as bad as the DC, but if it does then only expect the people in the lobbies to be hackers.
Why is duping bad I hear you cry? Well, a big part of PSO is trading and chatting. If you make a copy of an item, then you devalue that item because it is not as rare. Look at the Black King Bar situation. If that wasn't duped as much as it is, then it would be a rare find for anybody. But if you want one, you can probably just ask someone and they will make you a copy there and then. What is the point or trading if you don't trade legit items?
EDIT: typos
I doubt very much the GC will ever get as bad as the DC, but if it does then only expect the people in the lobbies to be hackers.
Why is duping bad I hear you cry? Well, a big part of PSO is trading and chatting. If you make a copy of an item, then you devalue that item because it is not as rare. Look at the Black King Bar situation. If that wasn't duped as much as it is, then it would be a rare find for anybody. But if you want one, you can probably just ask someone and they will make you a copy there and then. What is the point or trading if you don't trade legit items?
EDIT: typos

