Well now, here
is a pretty interesting site discussing the subject. The history of the principle is described... but that may only be "modern" history of VBL. It is easy to think that VBL requires modern materials, and therefore is exclusively modern.
Near the bottom of the page are some words emphasizing that the stuff really shines in VERY cold situations.
Here are some good quotes:
"Before you die of hypothermia from believing those false ads claiming their insulation is warm when wet, I suggest you soak you jacket in a tub of water, shake it out and wear it to experience just how cold it will really be!"
"What is warm when wet? A hot tub! But certainly not any porous insulation used in clothing or sleeping bags."
"To stay warm you must keep those insulations dry. It will not make you any warmer sitting in a freezing wet synthetic fill jacket, knowing it will only take 6 hours [to dry]instead of the 8 hours that a down jacket would take, because you would have a severe case of hypothermia before then!"
"You may have noticed that down is worn by water birds, while dry land birds, like chickens or turkeys, do not wear down. But those water birds always keeps their down dry!"
I hope it is as educational and fun for others to read as it was for me.