I've made this point before, but on a small scale (i.e., in discussing how many people actually contribute to a Wiki):

In most online communities, 90% of users are lurkers who never contribute, 9% of users contribute a little, and 1% of users account for almost all the action.

It apparently needs to be made over and over again - recall that Digg acted stunned by the idea that a small number of people were pushing most of the Diggs.

Go ahead and follow the link to Jakob Nielsen's site for data on participation rates.

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