I had the same deal in the U.P. a few years back. I was leading a group when I spotted a flashlight up ahead. Slowed down to find a dog sledder with a miners helmet stopped along the trail. He was moving his head back and forth(with the flashlight attached) to get my attention. It was snowing, we were on an old railroad grade, doing about 40-50, 10 PM on a Saturday evening. I shudder to think what would have happened if he had not stopped and turned around to warn us.
I have nothing against these guys....would love to do it myself.......but don't use the same trails please!