Growing up, I skied in various resorts in CO and NM, skiing in the trees or steep bumps. In the last 5 years living in the UK, I've been skiing in the Alps, going off piste whenever I can find good snow.
Two days ago, I had my most terrifying experience on skis. My friend talked me into skiing a couple of hours on an indoor slope not far from here, at 7:00 in the evening (when the place was packed with working stiffs and park rats at the same time).
On top of that, the beginner side was reserved for those taking lessons, which meant everyone else was packed on the normal side, and by "everyone" I mean all those people who don't really know what they're doing but won't spring for lessons. The slope was the equivalent of a good red in Europe or steep blue in the US, and by that time in the evening, it had developed a number of significant bumps and icy patches.
Honestly, I've never seen so many out-of-control skiers and boarders packed in such a confined space; it was actually frightening. I've skied in trees and amongst boulders and cliffs, but I've never been so concerned for my safety as I was on that indoor slope. I was afraid to stop at the bottom because I was certain someone would come crashing into me.
If you want to scare an extreme skier, stick him on a crowded indoor slope full of out-of-control people and watch him p*ss his pants.