People ski in the 50-60degree slope range all the time. Once you get over 60% it gets tougher, I think at around 70degrees that if you are standing straight up your elbow is touching the slope above you, thus making turns very difficult.
The stats you mentioned probably refer to grade, or %slope, rather than degrees. There is no 80degree ski run at a ski area. Yeah, Corbet's is definitely not over about 40degrees in the chute, the entrance is steep, obviously, but most of the steeps at Jackson are in the 40-50degree range.
Check out http://www.skiingmag.com/skiing/ask_...117389,00.html
, which explains the difference b/t degree of steepness and grade.