In recent years, many retailers have begun to sell pre-orders for upcoming games. They basically reserve the game for the customer who purchases the pre-order. To increase sales of pre-orders, many retailers and publishers have begun to offer exclusive DLC like costumes, weapons, vehicles, etc. or give an actual object like a t-shirt, soundtrack or artbook. Pre-order exclusives could also give the opportunity to play the game early through early access to demos or "multiplayer betas". Many retailers also have exclusive pre-order exclusives which can only be obtained by pre-ordering it from that specific retailer. For instance, one retailer might have an exclusive costume, weapon etc. for the game that wouldn't be available by pre-ordering it anywhere else.
Giant Bomb named this concept the Worst Trend of 2010.