@Nudhul @nugger @matty Guard dogs that you expect to experience violence ought to have their ears cropped. An ear injury in a dog takes forever to heal and has a greater risk of infection. If your dog is going to be protecting you from violent types on the regular, it's a necessary evil.
But if you have a guard dog for the home, and it's a family dog, then no cropping is necessary. Most dogs shouldn't have the operation (I didn't crop my dobie's ears).