Having Wikimania during [[Tisha B'Av]] [1], the last day of [[The Three Weeks]] is a
no go for all religious jews - not only Orthodox Jews. It is a long fast (26 hours long)
which starts the day before, very much like Yom Kipur.
Even I will not be able to attend Wikimania on that day (and the day before).
Deror
[1]
http://en.wikipedia.org/wiki/Tisha_B%27Av