Why do game mechanics work?
When designing game mechanics for a particular community, it is important to understand the underlying motivations and personality types that make up that community, otherwise the game mechanics may be ineffective at generating the appropriate user engagement. It all boils down to this: what some people find fun or motivating, others might not.
After defining the site’s goals, the designer’s next step to building a gamified site is to understand the community’s motivations. Attitudes, interests, age, and gender demographics all play a role (as seen in the Motivations and Personality Type sections of this site). Mapping motivations to various personality types allow the designer to select and modify game mechanics to best fit.
Perhaps in this respect it’s better to call them motivation mechanics.
For example, a single goal like increasing users, could be presented in different mechanics, each attractive to different motivations. This chart illustrates the mapping:
(Click chart for higher resolution)