1. A method of processing a transaction, the processing method comprising: responding to presentation of a portable consumer device at a reader adapted for offline processing by initiating operation of the portable consumer device, wherein the portable consumer device operates in a locked status or a not locked status; receiving data from the portable consumer device for a current transaction at the offline reader, wherein the received data indicates the portable consumer device is associated with a prepaid account balance for a prepaid product; determining at the offline reader that the prepaid account balance is in a negative balance condition in response to predictive processing that determines a next anticipated charge to the prepaid account balance and identifies a situation in which the next anticipated charge to the prepaid account balance will result in an insufficient account balance to cover the next anticipated charge; and taking preventive action at the offline reader in response to the negative balance condition such that future acceptance of the portable consumer device at any reader is prevented, wherein taking preventive action comprises issuing a lock command from the offline reader to the portable consumer device such that the portable consumer device is in the locked status and will be unresponsive to any reader requests for information after conclusion of the current transaction, wherein the preventive action is not taken if the prepaid account balance was not determined to be in the negative balance condition, and wherein the preventive action is initiated only by the offline reader.