Interesting post about the lack of participation in online communities by the long tail ( link here).
The Pareto principle says that 80% of the effects come from 20% of the causes. It is a favorite anecdote to cite that 20% of the employees in an organization do 80% of the work, or that 20% of the customers are those that generate 80% of the profits.
In online settings, such inequalities are often amplified. For Wikipedia we have the 1% rule, where 1% of the contributors (this is 0.003% of the users) contribute two thirds of the content. In the Causes application on Facebook, there are 25 million users, but only 1% of them contribute a donation.
Does this also apply to educators/trainers using online communities in the classroom?