Cropping is another (see docking) pseudo-veterinary procedure performed on very young dogs. It is a mostly cosmetic procedure, in which a portion of a dog's ear is cut off so that the rest of the ear stands up straight. So, for example, a ferocious looking doberman doesn't naturally have ears that stand up demonically, naturally they are floppy.

The American Kennel Club has this to say:
The American Kennel Club recognizes that ear cropping, tail docking, and dewclaw removal, as described in certain breed standards, are acceptable practices integral to defining and preserving breed character and/or enhancing good health. Appropriate veterinary care should be provided.
(Emphasis on the ludicrous mine.)

Note, dogs use the posture of their ears to communicate emotion. Cutting the ears off is at least partially akin to cutting part of a human's tongue.