It seems no matter how many times one mentions it in this thread, there will inevitably be another post at the bottom of the page knocking software because it actually showed mud roads as paved, ignoring the fact that this is not a feature the software offers.
While I always carry paper maps, anyone who feels mighty for using them strictly instead of these crummy GPS software programs is just silly. To be able to see your GPS location update in real time with the extensive road data base (among other options) is invaluable, and to say you'd prefer having your face in a paper map is either a lie, or someone who has never actually used either of these programs.
I've got Street Atlas and can rarely complain. Yeah, there are some new highways, or highway modifications that have not been updated but these are not day ruiners. When you get down to rural mud roads in the Great Plains, you get what you get. Having your face in a paper map or gazetteer is a good backup, but not something I'd recommend.
In the end, not allowing yourself to get into a position where "if this road ends for an unexpected reason, I will be in a potentially fatal situation" is the only way to avoid trouble. As has been mentioned, your roads can be impassable for reasons other than being plowed over (power lines, tree branches, construction, mud) and the only way to avoid danger is to not put yourself into the above mentioned situation. There is nothing like getting close to a powerful tornado, but you have to go about it in an intelligent and safe manner. Use your head. If the road you're on suddenly becomes unusable for any reason, what are the odds you don't have to drive across a farm field to avoid danger?
Time to get back to the early basics - always have an escape route.
I used paper maps up until 2007, but can't say I'd ever want to use anything other than Delorme when in the heat of the chase.