Yeah, when I did gymnastics, a lot of people used to wear Ugg boots to the competitions to wear before and between doing their routines, and in the long wait while the judges added up people's scores. (When you think Australia, you don't normally think 'sub-zero temperatures', but it did get this cold in winter in my hometown, and winter was when all the competitions were.) They're very good at keeping you warm, but they're terrible at withstanding the elements.

I can't imagine why people would wear them in the snow, though. They're not at all waterproof, and they have no grip on their soles. So you'd have shoes filled with water, and be falling over all the time.