Don't think I participated in the poker walk at Charleston WV (2001). I think the last one in Lexington was nice for socializing because of some of the outdoor vendors, including one with beer and food, along with some places to sit.
Those sites that had all the bikes in a parking structure (Charleston, Avon) usually had few people mingling around the bikes, but groups did congregate in other places. I think one thing that made Stratton better was people just hung around outside, in the front and around the groups of bikes. The weather helped, and the way the rooms were spread out sometimes you were better off walking outside (fewer stairs, skip the humid spa area, etc.). Maybe it was the variety of people, with more smaller groups from all over the country than the same large groups of people that may be more inclined to hang out in their own little groups.
I for one made an effort to not just sit in my room in the evenings, I fall into that trap sometimes. But since it was my brother first STAR I wanted to make sure we mingled ans spoke with lots of different people.
I don't think there is any one formula, but do feel the parking decks kill some of the "lets go look at bikes and BS" action that many people are interested in.