Duplication

Duping refers to the practice of use a bug in a video game to illegitimately create duplicates of unique items or currency in a persistent online game. Duping can vastly destabilize a virtual economy or even the gameplay itself, depending on the item duplicated and the rate at which duplication occurs. Duping is considered to be a game cheat.

DDO experienced multiple waves of duping. Many involved vulnerabilities in one or more of the following:
 * Bags
 * Shared bank
 * Crafting interfaces

Duping is against the rules. Players caught duping face temporary (rarely permanent) game ban and their inventories are cleared with.