Side by sides. They are literally changing places that I have gone and loved for decades. Not only do they tear up the forest service roads, but they drive everywhere. Why walk the 200 yards from the existing road to the creek? Just ride your side by side across that soft meadow! I was camping in a valley last summer during a scouting trip that used to be peaceful and quiet and it was a non stop parade of side by sides spinning and roosting the dirt road till the wee hours. Worse than that, one camp full of people was letting their kids drive the side by sides all day long, at one point they were literally doing doughnuts in the creek making the mountain stream muddy for miles. I've seen countless gates at the end of roads that have a side by side sized go arounds at them now.
I've got no problems with people who use them responsibly, but that seems to be pretty few and far between, giving them all a bad name.