I agree with much of what you say, however, there often is smoke in the air in the Sierra due to fires, both prescribed burns and wildfires that are left to burn out naturally. The FS here is pretty good about closing aras that actually are dangerous. If I were not to go out when there is smoke, I would rarely go hiking! If I choose not to hike when there is smoke, it is more that I do not like breathing it, and the views are compromised so taking photos is useless. I do not stay away due to safety reasons. The 50-mile limit you use is a bit more than I would use. And as far as seeing a plume of smoke - there are some areas in Wyoming that you can see 100 miles so it depends on how close that plume is. All in all, forest fires are something we need to be aware of and plan accordingly.