Customer Satisfaction Cannot Be Bought.
An awful lot of marketing is predicated upon the incentivisation of customers. Offer them financial discounts and/or perceived psychological benefits and they will buy your product/service.
In contrast, the Yale-based weight-loss site stickk.com is predicated on research that suggests that avoiding a negative outcome is much more of a behaviour enforcer. Facing a self-imposed financial loss if you fail to meet your target is apparently much more of a spur to continued action than being offered a positive reward.
The concept of opportunity cost which states that the true cost of something is having to forgo the next best option) seems to me to back this up and has been at the heart of my belief that not reducing customer irritation while avoiding blandness. A reward is nice, but inevitably short-lived. Having disappointment removed is less obvious but ultimately more noticeable.