Why Can On- or In-Pack Incentive Programs Like Pepsi Points

Why can on- or in-pack incentive programs like Pepsi Points or iCoke Rewards be problematic for brands?

A) The consumer may experience negative reinforcement when comparing competitive prices.
B) Retailers are not happy having to purchase large amounts of product to support the promotion.
C) Consumer switching behaviour is curtailed.
D) If the promotion is ongoing, it is difficult to predict consumer behaviour should the reinforcement ever stop.