The information was posted by the Yosemite park service and writtenup in various climbing mags. They also threatened
to fine those who had to be rescued who carried down garments
for insulation instead of synthetic. This was after a couple
of fatalities where the gear of goretex and down were considered
contributing to the deaths.

I don't suggest you carry a garbage bag instead of a goretex rain
suit, but if you are teaching kids (or others who don't have the
money for nice rain gear or the space to carry it when snowboarding or skiing etc) to survive a couple of nights out,
a garbage bag and a whistle tucked in their pocket or helmet
straps could make all the difference.

When skiing lifts in the northwest, you sometimes see people
skiing with garbage bags OVER their Goretex suits. Those
chairlifts can be pretty wet. A good rubber Uniroyal or
Helly Hansen rainsuit will keep you much dryer than Goretex in those conditions.