In this particular case, a woman caught out without suitable gear, the garbage bag made a critical difference.

Making this into a comparison between appropriate gear, in whatever for that takes for you, Vapor Permeable(VP) or not, and a garbage bag missed the point. I've never used a VP jacket that didn't cost considerably more than $100 and weight more than a pound. A garbage bag is roughly $.50, a fraction of a pound, and small enough to fit in a shirt pocket.

Should you accidentally find yourself lost in the woods, far deeper into it than you thought with night falling, you're not going to start turning out pockets and find a full-on mountaineering jacket. Much less a full suit, bivy bag and tent. Figure fifteen pounds, most of $1000, and big as a breadbox. If you turn out pockets and find a garbage bag you are in luck.

In fact it isn't an either/or situation. I've got bit and pieces of gear scattered about in outerwear I go to the mall in. Shaking out one of the lightweight shells I wear while camping I find a trash bag, a mini-Bic, a leaf bag, half a roll of Lifesavers, half a bootlace, and an acorn. You never know when they might come in handy. I'll be sure to stuff the Bic and the bag back in.

If she had a knife, lighter, and some wilderness skills she might have made a simple shelter and warmed it with a fire. The bag would still have helped but perhaps not been so vital. As it worked out she used what gear, strength, and skills she had and it kept her alive when others might have perished. When a survival situation rolls around your going to have to make due with what you have with you. A garbage bag stuffed into clothing your likely to have when going for a walk might make the difference. You might even stuff one into the pocket of your high-tech Gortex shell. It can be used as a groundsheet, tarp, or pulled over your legs as a field-expedient bivy bag. And even if its not a survival situation, say you stumble upon the mother of all mushroom patches, you have a bag to carry them out with. Lots of uses.