Moneyshot:

"The guy who started the larger of the two events emailed me several hours after I began posting links, and half-jokingly asked for “royalties”. How could I pass that up? I didn’t know what his privileges were as an event administrator, but I told him he would be subsidized if he could leverage the attendees (200,000+ at that point). He agreed[...]"

I see the above as the most important factor in the huge success! It would be interesting to hear if guynamedloren agrees with this.

Generalizing: One should attempt to achieve exclusiveness in the promoting medium.