I just remembered a good one. I have a pic of lovely cottage with a fresh snow covering the porch and ground. It's a pretty scene. If you look closely through the open front door, you can see a wood stove... covered in snow with debris around it. All that was left standing was the front wall.

It took me about a minute to spot the cause of the roof collapse. The gusset plates on the roof trusses were pressboard (chipboard, other names). All it took was a bit of freeze-thaw and a medium snow load.