This thread has me thinking of that BBC television series with Ray Mears, predecessor of sorts to Survivorman and Man vs. Wild. One purpose of Mears' show is to teach survival techniques in various environments where one possesses a minimum of gear, i.e. no sleeping bag. What he almost always does have, however, is a huge axe. Elaborate shelters and large fires are constructed by Mears at great expense to the surrounding flora and fauna- trees, ferns, moss, etc. Sure, says Mears, you can sleep without a sleeping bag, but it will require a six foot long fire trough burning all night. This technique could come in handy, but it is clearly not a practical solution for regular backcountry travel in LNT style.
I realize that if survival is at stake, it is sometimes necessary to compromise Leave No Trace ethics. Furthermore, Mears generally puts himself in out of the way places where his overall impact is probably fairly negligible. However, for me the show highlights another function of gear in the backcountry beyond maintenance of life and limb: gear helps us maintain LNT ethics. With adequate insulation and a stove, one can exist in the backcountry without disturbing your surroundings, particularly in fragile environments such as those found above treeline, or areas that experience high levels of use.
I don't mean to imply by any means that anyone here is dispensing with or violating LNT ethics. Pushing the limits of gear, or lack thereof, is an interesting challenge, and no one is dispensing with their sleeping bag while sharpening their axe! Furthermore, I don't want to get involved in a discussion of different views on how best to apply LNT ethics, or whether particular lifestyles or ways of traveling are LNT or not. It is only to say that while pushing the limits of ultralight travel, the question should be about both personal comfort/safety as well as one's ability to travel through the backcountry in an ethical manner. This includes a consideration of the sacrifices that must be made if gear fails or is inadequate to the task. Probably all the more reason to test the limits in conditions where massive quantities of hot chocolate and pancakes are relatively close at hand!