Wikipedia survives and even flourishes in its open environment, mostly because the builders have been, at least so far, more dedicated and persistent than the vandals. A vigilante army of self-styled Wikipedians defend the site and enforce community policies based on the principle that Wikipedia is an encyclopedia and not a forum for advertisements, slanderous remarks or pictures of your cat. They police the site to try to establish a neutral point of view, warn users against violating copyrights, and call for respect toward the contributions of others. Wikipedians also have a secret weapon built into the site’s software, which saves every version of an article and allows users to reinstate an older version with a simple click of a button. If I were to replace all the text in the entry on “influenza” with the phrase “my cat’s breath smells like cat food,” the wit and wisdom of Ralph Wiggam would not be likely to last long. Diligent, sleepless Wikipedians would swoop in and revert the page to its previous version. According to the Wikipedia’s vandalism entry, “A 2002 study by IBM found that most Wikipedia vandalism is reverted within five minutes.”