1) People who are utterly ill-equipped and know nothing. Almost all of these are within a mile of the trailhead. They are very unlikely to experience worse than an unpleasant time.

2) People who are underequipped and know little of the local situation. These are almost all tourists. (To date I have encountered only one exception--two guys 4 miles and ~2,500' in, water bottles and big, heavy sticks that were worse than useless as trekking poles. Fortunately I got them turned around, had they continued they would have been out of water, risking hypothermia and have had no chance of getting back to civilization before dark--and they had no light.) The ultimate example was a guy from Florida. He was asking me for navigation advice, attempting to reach the highest local summit. It was his 4th attempt, the previous three were blocked by snow. By unreliable reporting there were several feet of snow on the summit at that time, it certainly wasn't considered passable. He was asking me about a third trail shown on his map. Really now, an arrow-straight trail in steep mountains?? That's the boundary line for the ski resort! No GPS, no poles, if he by some miracle summitted he would have had no chance of getting down before nightfall.