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Wired runs a nice round-up on the ways you can manipulate wisdom of online crowds -- community-scoring systems -- in your favor. These ways are:
1. Invest in building your own group of power users.
2. Buy the votes.
3. Identify existing power users and link-bait them
4. Build your reputation on small transactions to cheat on the big ones.
Here's a bonus story about an experiment in crowdhacking: the articles author tests how effectively one can drive traffic by buying Diggs on Users/Submitter.
Earlier:
Pay To Get Dugg
Reality Check: Community-Governed News Sites