1. A system for incentivizing users to alter virtual item balances in user inventories in a game space, the system comprising: one or more processors configured by machine-readable instructions to: execute a game instance of a game space, and to implement the game instance of the game space to effectuate transmission of information over a network to client computing platforms associated with users that causes the client computing platforms associated with the users to present views of the game space to the users, and to enable interaction of the users with the game space and/or each other by performing operations in the game space in response to commands received over the network from the client computing platforms associated with the users; manage user inventories of virtual items associated with individual ones of the users and the game space, the user inventories indicating balances of a first virtual item usable in the game space associated with the individual ones of the users such that a first user inventory indicates a balance of a first virtual item associated with a first user; enable users to spend virtual currencies within the game space in exchange for virtual items usable in the game space; obtain current balances of the virtual items indicated by the user inventories, the current balances including first current balances of the first virtual item indicated by the user inventories associated with the individual ones of the users; dynamically determine, based on the current balances of the virtual items obtained, balance goals for users to reach target balances of the virtual items in the user inventories associated with the game space, the balance goals including a first balance goal specifying a target balance of the first virtual item to be reached in the first user inventory determined based on the first current balances of the first virtual item indicated by the user inventories associated with the individual ones of the users, the first balance goal further specifying a time by which such target balance must be reached in order for the first user to receive a reward; review the balance of the first virtual item in the first user inventory and determine whether the first user has reached the target balance of the first virtual item in accordance with the first balance goal determined; and distribute a reward to the first user inventory associated with the first user and the game space responsive to a determination that the first user has reached the target balance of the first virtual item in the first user inventory in accordance with the first balance goal wherein the reward is distributed to the first user irrespective of a purchase or achievement within the game by the first user and distribution of the reward causes the first user inventory to update to include the reward without depleting the first user inventory.