The second stage of crowdsourced gamification is to create "horse races" within the tribe. Important to race apples against apples and not apples against bull dozers. Each player must feel as if they can accomplish their goals.
See Scoop.it community for this idea of segmented leaderboards handled perfectly.
Play should be combined with "a job" or early adopters may leave after achieving initial objectives (FourSquare's Mayor or reward burned out since it was insufficient to maintain game play by itself).
The "job" for most early adopters is to become "brand advocates" and "hall monitors". Good idea to give real responsibility to early adopters as they transfer from game play to game monitors and UGC contributors.
Games Create Acceptance, User Generated Content & More Play.
The not so hidden secret of great business gamification is the real goal is to heighten the desire for more game play. The risk is rewards will need to ramp in a way that can wreck a business P&L or be insufficient as "continue play" rewards.
Finding the balance between rewards, reward sequence and the mix between social and material reward is highly variable and based on things like why the game is being played in the first place (what psychological need is being met).
Play can be a constructive or destructive force. If more play weakens or implodes the reward system more play was harmful (except in tuning the system).
More play should always create greater circles of ante (advocacy, shares, cash). When in doubt give more and more of a game's framework over to early adopters who've moved into hall monitor and contributor roles.
One of the hardest Internet marketing lessons is the product you THINK you are creating is secondary to your ability to create any online marketing. Online marketing is a complicated branching process that takes amazing timing, skills, experience and luck. The most valuable engine is not what most teams think they are creating - a website about something. The most valuable product is always a team capable of understanding the web well enough to create anything at all.