Everyone has pointed out, correctly IMO, that the basic problem was over reliance on technology.

I don't think the problem is with the use of GPS, though, I think it's a lack of familiarity with driving in the snow. On the road, especially in flat country, 2" of snow looks a lot like 6", which looks a lot like 2'. Someone who has some degree of familiarity knows when they're in a situation they shouldn't be. I don't know if someone who has never driven in snow would realize the problem until it was too late?