I was riding with a buddy yesterday through mostly woodsy trails, a lot of which were covered in ice and snow. We both brought our winter snow-tired bikes. His is a Bridgestone MTB w/ lots of clearance between tire and clip-on rear fender. Mine's not. So a well placed stick as I was cruising along made its way up my back tire and took the fender along with it, at which point I came to a stop.
But all was not lost as I was able to do a reasonable job of straightening the fender out after I took those pics above.
Not exactly showroom quality, but it'll work for my commuter bike.
Neal