I usually name them all. For one thing, if I come in and tell Ken that one of the chickens is acting funny, he's immediately going to ask me, "Which one?" Kinda hard to tell him the one with the wings, two feet and a beak and have him know which one I mean. Also giving them names sort of says, "I recognize that you are an individual."
However, that kinda went by the wayside when I got chickens who look alike. Two Easter Eggers grew up to look identical. We just call them "the Twins". The other 7 I can tell apart easily and they are Daphne, Mathilda, Agatha, Gladys, Bumblebee and Frog. The Red Sex Links can be a little tough to name and keep straight unless you know the white patterns on them. They are Ida, Dora, Cinammon, Nutmeg, and Ginger. Oh, except during molting. Then each one is simply known as "that one over there." Only one Buff Orpington and she's Kat. Two Cuckoo Marans, Cora and Edith. But then comes the Brahmas. Oh, dear. I have 4 Lights and 8 Buffs, and I can't tell them apart at all. So the Lights are named One, Two, Three, and Four. I have a one in four chance of calling them the right name when I'm out there. And the Buffs are Sheuster, Brewster, Rooster, Booster, Moose-ter, Goose-ter, Juice-ter and George. If I go out and call "ooster" one of them is going to come anyway. George, well, she'll just have to deal with her identity crisis on her own.
Charlie, Floyd, Speckles, Big Red, Little Red, and Scout are all in the freezer. Daphne will be joining them soon. I guess it's plain to see that naming them even if we are going to eat them doesn't ruffle our feathers.