*People are always trying to make bags out of goretex and stuff, and you really don't need breathable for the whole bag.*

I've never heard of any bags that were made with goretex..even backpacking packs. And as for people building their own bags with goretex - I'm pretty sure it's next to impossible to get your hands on the actual material (which is a thin white film) and even if you did you'd need the equipment to apply the goretex to the fabric.

Also - as much as goretex and the industries that use it claim it's breathable..it's really not all that.