Figure I'll post this here as well, because, well, I can. Since Scott McNeil (VA of Flam, Thunderhooves, Rover) was attending this recently passing Youmacon (Nov.1 — Nov.4, Detroit, MI @ Renaissance Center & Cobo Hall) and there was mention of a meetup last year on EqD that came to no known fruition, I wound up organizing one myself.
After 2 months of advertising/preparing, support from con staff and guests (such as MasakoX, Nowacking, and 8-Bit Mickey), etc, it happened and, for a first attempt in which we promised nothing other than to meet at the designated spot during the con, I'd say it went pretty well.
I'd guess we had about 70 people at the most at any point in the meetup, sans MasakoX and Nowacking who had scheduling conflicts, but we had about 50 people here, when we decided to take our planned group photo. Even though Mickey was only able to make it 10 minutes after our meetup came to a close and stay just long enough to take another photo, he was pretty impressed with what I and my 2 fellow hosts accomplished on such a whim, and is helping us plan further Youmacon meetups/projects in the future.