It sounds like a chaotic day, and it makes me wonder how the marathon officials dropped the ball on having water/gatorade available in that size marathon. But I remember a 10-mile race in my area that was unseasonably hot several years back, where aid stations were out of water. Just as in Chicago, some folks were running into stores to buy bottles of water. I had a very, very slow race (although my training indicated about 8:40ish pace, I ended up doing about 1:40something), also got dizzy and needed med tent help at the end (fortunately, recovered fast). I was prepared for the distance, but not for the conditions. Since the race was only ten miles, and there weren't nearly as many people as in Chicago, it wasn't as disastrous an affair, but even there, I had to wonder how the race people didn't anticipate w/ the weather forecast the need for more water/Gatorade on the course.
Just IMHO, I won't even attempt a marathon in such weather. My hat's off to people who can run well or run at all, for that matter, in hot, humid marathons. And if I were one of those folks and had felt up to finishing, even if slowly, I would have been sorely disappointed to be ordered to stop and walk, especially if there had been no announcement made before the race that this was a possibility.
A better alternative that Ironman events and longer ultras use is to have certain checkpoints announced in advance that people have to reach at certain times and make the rules clear before everyone sets out. So, there could be checkpoints at, say, 10k, halfway, and 30k or something of the like, and people would KNOW before starting that they had to reach those checkpoints to be allowed to continue. It seems to me that would make a lot more sense than just wholesale stopping a race in the middle, which just seems to guarantee chaos. And how much safety does it ensure when suddenly people are told the race is canceled and maybe they are having trouble but are now on their own?
Just a few thoughts... .