I was up in the Porcupine Mountains wilderness area (atate-managed land in the Upper Peninsula of Michigan) last week and saw several of them -- some very large with elaborate camera setups. At a distance, they were only mildly distracting, but as they came in to their controller, they sure did put up a buzz.
Interestingly, a park ranger came up the ridge while I was there and asked them for their permit. When they said they didn't have one, he simply told them to get one the next time, and went back on down. I'm betting something like this happening on Federally managed land might not be resolved quite so mildly (or cheaply).