Hi,
There is an interesting discussion on wikitech-l about statistics. Tim has already generated some data - I collected the graphs at
http://meta.wikimedia.org/wiki/Days_since_first_edit
and wrote something about it in my blog at
Because there still seem to be people that are not aware of the steep distribution of activity per contributor: It's confirms [[Lotka's Law]] - at least for the majority of contributors - a power law in the form "contributors * edits^1.5 = constant" (see page 56f. in my masters thesis [1]).
Greetings, Jakob
[1] http://jakobvoss.de/magisterarbeit/MagisterarbeitJakobVoss.pdf (in German)