Pygmalion effect

People tend to behave as you expect they will.

Named after the Greek myth of Pygmalion and his statue. George Bernard Shaw wrote a play, Pygmalion, which has later been popularized by the musical My Fair Lady. The character Henry Higgins believes the cockney flower lady Eliza Doolittle can be made into a "lady". Higgins' belief in her drives her to make it.

In Eliza Doolittle own words: "You see, really and truly, apart from the things anyone can pick up (the dressing and the proper way of speaking and so on), the difference between a lady and a flower girl is not how she behaves, but how she's treated. I shall always be a flower girl to Professor Higgins, because he always treats me as a flower girl, and always will, but I know I can be a lady to you because you always treat me as a lady, and always will."

Translated into a wikipedian setting: Wikipedia users will behave because Wikipedia expects them to.