I have mentioned my observation to other people on a number of occasions, usually to denial. However, last week I saw a similar sorting in the BioInformatics conference room. The first day the speakers were not particularly compelling, and most of the attendees sat near the back of the room; the second day the topics were much more interesting, and the attendees distributed themselves much closer to the front. I commented on this distribution to the gentleman across the table from me, who happened to be a geographer, and he cited some research in support of my observation.
It happened back in the 50s, they randomly assigned students to seats in a classroom and required them to sit in their assigned seats the whole term. Because the seating was random, there was no geographical component to student ability or grade point average going in, but at the end of the term there was a significant geographical distribution of the grades in that class, with the students in the front doing better than those in the back, and those in the center doing better than those on the sides. This is of course different from the self-sorting that goes on in church congregations and conference seating, but apparently related to it.
Last night at church the usual distribution was inverted, with the greatest density of people near the front, and the back rows almost empty. The program was unusual too, the first time they ever did a talent show kind of thing, with large numbers of people (including a whole bunch of kids) taking turns getting up front to perform. I guess watching your family or friends show off is more interesting to the average church-goer than the regular hymns and sermon.