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The Wikipedia community relies on the No Original Research core policy to combat unsubstantiated claims from finding their way into articles:

Nutshell http://upload.wikimedia.org/wikipedia/commons/c/ce/Nutshell.png This page in a nutshell: Wikipedia does not publish original thought: all material in Wikipedia must be attributable to a reliable, published source. Articles may not contain any new analysis or synthesis of published material that serves to advance a position not clearly advanced by the sources.

The very purpose of this site as defined by the FAQ contains nearly exactly the same idea (my emphasis):

Skeptics - Stack Exchange is for skeptics, rationalists, free thinkers, or anyone who questions pseudoscience. Skeptics is about applying skepticism — it's for researching the evidence behind the claims you hear or read.

The voting system of Stack Exchange is largely meant to relax any need for specific policy regarding what constitutes a valid answer (and by and large it accomplishes this) — however, due to the nature of Skepticism, the community (and perhaps the FAQ) ought to promote the idea of no original research to encourage healthy voting.

Bad: (all seen in answers here)

  • "...since I have personally experienced it numerous times"
  • "Anecdotally, I've seen it..."
  • "I heard that it was also caused by ..."
  • "I'm not sure if this idea comes from some research"