I would like to nominate Jim BelkJim Belk. He was very involves in the conception of the site, from the very start on, and continued his involvement ever since.
There were already some occassion where he and I did not have the same opinion, but in all these situations of disagreement I felt his behavior was exmplary. Thus, in addition to knowing from his contributions here and elsewhere that he is knowlegable and passionate about communicating mathematics, I feel I can also claim from first hand experience that he has the right personality to moderate a site.