But to be money rather than "money," an exchange medium must be generally accepted in exchange, not just among the members of a certain group. Among players of certain online games, certain digital items circulate as exchange media within the game. They function as money in the game, but are obviously not really money. Until it is generally accepted in exchange -- which it will not be -- it is not money. Money is what is generally accepted in exchange. Collectibles like art typically do not yield any income, only a capital gain, so they are speculative vehicles rather than investments.