 Others have stated that a measure like accounting on average cost basis would restore fungibility to the currency.Virtual currencies have been called "closed" or "fictional currency" when they have no official connection to the real economy, for example, currencies in massively multiplayer online role-playing games such as World of Warcraft.While there may be a grey market for exchanging such currencies or other virtual assets for real-world assets, this is usually forbidden by the games' terms of service.