The worst fogging I've ever had was with my Anon Insurgent goggles about 3 weeks ago. It was like -10ºf and the fog on the inside of my lens froze before it evaporated. It gradually got worse until it was like I was looking through frosted glass. I eventually went in to the lodge until they defrosted and I shook them out.
I've worn them a few times since and not had fogging problems at all. Not sure what the deal was.