Before we get into another "ultralight" thread that needs to be moderated by closing it down lets get some perspective.
This "pack light" mindset comes mostly from trekkers hiking the long trails in a single season. They are not doing an overnight or a few days, they are hiking substantial miles almost every day for months. Some here on BF have hiked these in a season and it is a serious outdoor accomplishment. For those that are not aware, the USA long trails are:
The
Appalachian Trail Georgia to Main 2,160 miles
The
Continental Divide Trail Canada to Mexico 3,100 miles
The
Pacific Crest Trail Canada to Mexico 2,650 miles
The AT is pretty well worn, the others are far different. Google them to see the routes and terrain. When you need to pack an ice ax and crampons you are not going for a walk in the park.
The point is, these people that hike a distance of 2,000 - 3,000 miles in a Spring to Fall season have some ideas about what works for them. I may not agree with each "ultra light" choice and may think some are downright foolish but I will respect that they know something about what they are doing. After all, you get plenty of time to think when you are hiking sunup to sundown every day for weeks on end.
Here are two short articles by way of Google about some long trail accomplishments...
http://www.washingtonpost.com/wp-srv/aponline/20011027/aponline213001_001.htm
http://www.americanprofile.com/article/19331.html