My thoughts on trail runners are those guys/gals are respectable! I love to go backpacking and have spent up to a week at a time on a trail. But these trail runners will do the same trail I do in three days in just one day! That's pretty amazing. It must teach amazing foot-eye coordination because there are so many "obstacles" on a trail that could potentially be a twisted or broken leg.
I have never had any problems with encountering trail-runners along the trail either. They are typically very nice and will go around me. So, in summary, I truly respect the ability of trail-runners and have no problems sharing the trail with them, but I think I'll stick to walking myself!!
