On the other hand, we hear of the occasional Good Old Cruising Boat, plodding along, that suddenly sustains rudder damage from unknown causes and sinks in minutes. Rare, maybe, but not unheard of. More rare, probably, than some vociferous advocates of the full-keel school might have us believe. I just find it weird that relatively simple precautions, used at the pointy end of the boat, are not used in the back.
Rather than extreme sailing forces, my imagination suggests something more like a whale that decides that the nice pointy thing sticking out there is the perfect thing to scratch his back...