I appreciate the feedback here.
To repeat-- this idea is not about segregating people. It is about making it easier for people to focus on areas of high interest and get information more easily. As I pointed out from my own experience, the regional forum I have posted in the most is the Northern Rockies even though I live in Virginia. I am glad I do not have to sift through all the Colorado threads to find threads about Montana and Wyoming; it's with that in mind that I asked about splitting Utah out from the Southwest.
When I have the time for it, I will make a Utah forum and start moving threads there. Time and user feedback will tell if it's necessary to split up the East and/or the Midwest.
The ideas about splitting according to physical rather than political geography are good ones, but since that's not how the forums were set up here in the first place, I think adding that now might be messy or confusing, with the lines often difficult to draw.