After doing some googling I found an article [1] that provides a somewhat more nuanced view. While it is true that around 70% of the edits each month are generated from the top 1% of users, this is only true for the top 1% of that month. When you look over a longer period the majority of edits come from users with less than 100 edits in total (which seems to be around 90% of the population).

[1]: http://asc-parc.blogspot.nl/2007/05/long-tail-and-power-law-...