It seems to me that most of the really famous mountaineers carried very large knives with them for building shelters, fighting off bears and such. I have read that "Grizzly" Adams, Daniel Boone, and Davey Crockett all carried very large knives, some with 11" blades. The early Native Americans also seemed to be in favor of the large knives such as the 10" Dag Knife and the Hudson Bay Camp knives. However, I do think they also carried with them smaller knives for carving, eating and small chores. I suppose for many of today such a large knife would seem heavy and burdensome, but for them back then, it was probably not a big deal. Thems were some tough dudes back then... I think 4" knives are a great size for carrying around, going hunting, or whatever, but if I were actually stuck out in the wilderness somewhere for some time, I would want a knife that was a little more substantial. Something I could knock a bears teeth out with.
Oh yeah...those Vikings also and their large knives like the Scramasax.
Basically, if I were to live off the land and fend for myself food and shelter, I would rather look to history and what they used for extreme bush living/survival/camp knives back then as my reference. I would not base my knife selection on what some modern day "survival experts" think is a good knife. I think big knives were used and favored back then for good reason. If Daniel Boone were alive today, he would probably take one of those small 4 inch "bushcraft" knives and use it for a toothpick.
I think there is a difference between extreme outdoor survival and the more leisurely and perhaps modern "hunting/fishing/camping" scenario. It is like the difference between fighting off Grizzlies and chasing squirrels.