  Human communities have self-organizing properties in which specific Dunbar
Numbers may be invoked to explain group attachments. By analyzing Wikipedia
editing histories across a wide range of subject pages, we show that there is
an emergent coherence in the size of transient groups formed to edit the
content of subject texts, with two peaks averaging at around $N=8$ for the size
corresponding to maximal contention, and at around $N=4$ as a regular team.
These values are consistent with the observed sizes of conversational groups,
as well as the hierarchical structuring of Dunbar graphs. We use the Promise
Theory model of bipartite trust to derive a scaling law that fits the data and
may apply to all group size distributions, when based on attraction to a seeded
group process. In addition to providing further evidence that even spontaneous
communities of strangers are self-organizing, the results have important
implications for the governance of the Wikipedia commons and for the security
of all online social platforms and associations.
