Being caught out, unprepared, in bad weather.
A good quote from the above article rings true. “Most trails are not marked for winter use, so navigation can be challenging“. Even if you are experienced, a blanket of snow can make staying on trail a challenge. Make sure you have a good topo of the area, a map, a GPS, and the skills to use them. The $1 trail maps you buy at a trailhead, do not count. Large scale maps do not show land features, topography, etc. and can cause you to second guess your whereabouts like the interviewee said last week.
Mytopo. Custom printed maps of your area: http://www.mytopo.com/
Nat Geo maps: I carry one of these because I cover such a large area: http://www.natgeomaps.com/trailsillustrated