My 2 cents on corrals and self-seeding, etiquette, etc.... I'll hazard to say that 99% of accidents and annoyance in rD races come from people simply not paying attention and not being respectful of others on the course. I've started in a gazillion different corral letters over the years, and I promise - stuff happens regardless of where you start. As mentioned, rD races are unique in that they have so many people constantly exiting and entering the course for photo stops, and that inherently leads to people of different speeds intermingling on the course, no matter where they happen to have started. Add in the usual amount of "bad drivers" we find in every day life - those who don't look around them before merging or changing "lanes, who barrel though congested sections when traffic around them has slowed down, who generally act entitled and irritated by those who are doing their best to keep up with traffic and not get "in the way" - and rD races are simply always going to be different beasts than other races. Frankly, I no longer have much sympathy for the inevitable complaining. The vast majority of us are out there doing our best to juggle unusual running conditions, our own abilities, and the desire to have a good time - we'll ALL have a better experience if we chill out, accept the realities of running Disney, and let the inevitable accidental mishaps go.
FWIW I nearly always start in the back of my assigned corral. I hate crowds and starting back there means having the course nearly to myself for the first couple miles: the people in my own corral all take off and by the time fast folks from a couple corrals behind me catch up, they've spread out considerably. I'm also a slow starter, fast finisher, so starting in the back makes it easier/more comfortable to race my own pace from the start.
