I regularly read the articles here, but haven’t participated in the forum community. I registered to comment on this thread cause a friend I introduced to equipped poked me.
A couple of specific responses:
(1) Hiker Jim said "Well, for the record no one that I've ever heard of does 50 - 60 miles in a day.". Well Jim, there are a few people I know who have done this... thought most were typically doing their 200+ miles as an ultra-marathon with support stations rather than as a more traditional hike. There are plenty of ultralighters who do 30-40 miles / day for an extended period of time. Several have done one of the long trails likes the PCT with an average speed on ~30 miles / day which includes rest days and stopping to resupply. These folks do hit 50 miles on some of their longer / faster days. Personally, I won't go this fast because I doubt I am capable of that rate of travel, but also because I found that I like 15-20 miles in a day. More than that seems rushed.
(2) ironraven suggested that "Most ultralighters have no back up plan if something goes wrong." That is not the case with most of the ultralighters I know, and I know a lot having been part of that community for something like seven years. Admittedly, sometimes the backup plan is to "be cold and wet"... but not so cold or wet that it puts the person at serious risk given the conditions. All of the ultralighter I know or have corresponded with bring firestartering materials... though sometimes the firestarting material might have other uses. I know of no ultralighter who carries less than 1L of water unless they are someplace that has an abundance of water. Most ultralighters I know do use some sort of purification (aqua mira seems to be the most common), though some forgo purification in placed deemed to be low risk. As was cited earlier, there is some decent evident that the water is pretty safe in some locations without purifying. I have talked with several backcountry rangers in the sierras (carrying heavyweight packs) who have forgone purifying their water for years without a single incident. Not having rain gear over their legs and wearing shorts? Guilty on some trips because when I am on an ultralight hike, I spend pretty much all my time hiking. While I am hiking I am warm enough without pants or rain gear. Remember, your legs are pretty much waterproof and dry very quick, and wearing shorts avoids getting pants wet which take a long time to dry. So I am active until I stop, I quickly set of my shelter, dry my legs, and then put on additional clothing and/or get under my sleeping quilt. As to everything is made from ultralight materials that can't take off trail use... Well, sort of depends where they are hiking. If folks are hiking on trail those "ultralight" materials are good enough. There are several people who have 6000+ miles on one of those <1lb silnylon backpacks. I would say that not bad. There are plenty of ultralighters who do go cross country. Many ultralights switch from the gossamer spinnaker cloth or light silnylon to something like dyneema grid, 100% spectra, or VX-21 core fabrics.
Now to general issues.... There has been a lot of misconceptions about ultralight backpackers on this thread. Sure, there are some wildly irresponsible ultralighters who don’t bring what they need and might really be putting their lives as risk… but this is rare, and I think it has nothing to do with “ultralighting”. It has to do with some people being stupid… hence things like the Darwin awards. Several times I have helps ill-equipped people get out of the back country. It's never been an ultralighter. It has been heavy-weight packers who exceeded their ability to cope (and didn't plan well), or folks who hiked in 10 miles with a cooler filled with beer and potato chips, and a blanket over their shoulder, and realized they were in trouble as night started to fall.
First, I would like to remind everyone that life is risky. Complete safety is an illusion, and even if it wasn't, it would be so bore that I wouldn't want it. Life involves risks, what is important is to balance the risk/reward tradeoff. Some ultralighters might be willing to accept a bit more risk to achieve their goals than people on this thread are comfortable with... but I think the risks they are taking is actually smaller than the risks they take crossing a busy street in the city.
Second, lets make sure we separate "safety" from "comfort". It is possible to be uncomfortable, even in pain, but still be safe. All the ultralighters I know are extremely thoughtful individuals who are aware, typically based on extensive experience, of what is needed to be reasonable safe, and don't step over that boundary. Many ultralighter are willing to forgo some amount comfort to achieve their goals. Pick any sport or activity and you will find highly regarded individuals who felt it was worth some discomfort to push the boundaries. For example, the teenage Jack Nicholas practiced his swings even after his hands bled for the activity. There was some risk... for example his abused hands ran a great risk of getting and infection... but that was a modest risk and worth the payoff to him. Likewise, ultralight hikers typically take reasonable risks which might leave them uncomfortable in some situations, but not at an unusually high risk level.
Third, just because an ultralighter isn't bring enough stuff for YOU to feel comfortable doesn't means that they are uncomfortable. I like my comfort. I spend most of my time on my feet hiking. Typically the only thing I do in camp is sleep. So for me, comfort is mostly about the hiking... less stuff is more comfort. In camp, comfort is about being warm, dry, and getting a good night sleep. For me, a tarp, down quilt, and on most trips and insulated air mattress provides that and weights less than 3lbs.
Fourth, my experience with survival, first aid, staying safe, etc... is that the most important item is your brain. I have seem people with a pile of stuff get themselves in a world of hurt because they didn't think. I have seen people with what I thought too little stuff do better than anyone else when facing a challenging situation. At it's core, ultralight is about using knowledge, techniques, and experience to leave stuff behind that isn't needed.
So how does this all work out? Let me give one small example. I have been on several trips where people were sure I didn't have enough clothing, and worse, I had what they though was a completely inadequate 1lb down quilt to sleep under. They were sure I was going to be cold. They were wrong. Why? First, I have learned that I run a bit hotter than some people, but more to the point, I had learned through careful observations what I need to start warm and comfortable. Like maybe people who switch to an ultralight style, I started out carefully. I would commit myself to use what I thought was the right "ultralight" mix of clothing, but I brought a drybag with "emergency" clothing that I would take out if I moved from uncomfortable to "at risk". I was willing to be chilled so I would know what MY comfort range was given physical environment, clothing, and my physiological condition. [One of the things I learned was not eating enough of being really tired meant I needed more insulation.] If you don't push into uncomfortable you don't really know what your limits are. If you are unwilling to stay uncomfortable for a while you won't learn how quickly you acclimatize (some people takes weeks, others days). After carefully monitoring my comfort, conditions, and gear, I have dialed in exactly what I need to be comfortable for a given set of conditions including a safety margin which takes into consideration the variance a specific location is likely to have. This didn't happen over night. It involved a fair amount of research, experience, and experimentation. To me it's worth it. In my overly prepared days I carried a 60lb pack and I found 10 mile / day trips exhausting and painful, but worth it because of the places I got to see. These days I am carrying a 10-30lb pack depending on conditions and length of trip, can easy hiking 20 miles in a day without feeling fatigued. One of my notes on this can be found linked into
http://www.verber.com/mark/outdoors/--Mark