Was it a blatant cutting of the course, or just a misread of the trail?
There's one switchback in particular above tree line that has that HUGE rock (I know, they all have HUGE rocks!) and a major step up (or step down) if you miss the turn. I saw several people miss-read this switchback on the way down, and inadvertently cut the switchback. It was obviously unintentional, and totally understandable for those that may not live here and don't spend a lot of time on Barr Trail other than race day. This particular mistake is not a major one because the place where most people mess up is just a few feet from the actual turn, so at best it may cut off about 5-seconds.
I even witnessed one downhill runner miss this switchback and realize immediately that he had done something wrong (but not quite sure what). He got all twisted around and actually started going back up the trail!
I've been up Barr Trail over a hundred times, and I still miss that darn switchback once in a while if I'm not paying attention.
We should probably make a note to find a way to mark that switchback better in future years. It's the most confusing one on the entire course as far as I'm concerned.