Continuing the geek vibe, I believe the best starting point to make sense of inner workings of incentive systems and rewards is SDT - Self-Determination Theory. It's 70+ yr old theory of motivation in psychology that originated in studies of how external rewards (i.e. tips or bonuses) crowd out intrinsic motivation.

In other words, if we want employees to act friendly to customers - should we design a system of external motivation (rewards and punishements) or design a system that boost intrinsic motivation for this behaviour. For example, SDT has many studies on how different rewards giving patterns affect motivation. As far as I remember, the least detrimental is task-noncontingent rewards (giving "reward" for just "showing up", basically). The most detrimental to motivation is competitive-contingent (give reward to those who outperform others).