Maybe I should have looked closer at that page before I linked to those anecdotes in particular. I chose it because there were lots of anecdotes, and it was convenient. To show that these don't constitute all related anecdotes, since that might not have been clear:

Amy Short from Brooklyn, N.Y., tells WebMD that she began feeding her domestic shorthaired cats, Olive and Georgia, a commercial vegan diet as 3-month-old kittens. “Because I am a vegan, I strive to live my life as compassionately as possible,” she says. “I had real dissonance with the idea (and brief practice) of buying animal-based food for my pet animals.”

Besides a little dental trouble for Georgia and springtime allergies for Olive, Short says the cats, which are now 8 years old, are “healthy, happy.”

http://pets.webmd.com/features/vegetarian-diet-dogs-cats

Now artists and activists (with one more feline in the family) in Ithaca, N.Y., Moore and her partner, Shira Golding, are part of a relatively small but deeply dedicated group of vegan pet owners who believe their cats' and dogs' diets should reflect their own beliefs about the treatment of animals and environmentally sustainable lifestyles.

Despite the anecdotal evidence the group has amassed that supports vegan pet diets, many veterinarians are reluctant to recommend the meatless option.

http://abcnews.go.com/Technology/AmazingAnimals/story?id=7154396&page=1

Gillen makes the point that at the very least vegans should try vegan cat food and see if their cats like it. He ends the book asking people to at least meet him halfway - feed your cat meals that have at least some vegan food mixed with the other food.

http://www.amazon.com/Obligate-Carnivore-Really-Means-Vegan/dp/0974218006

It's was just relied on self reporting and was not done in a controlled environment.

Did you actually read the article? Regardless, here's a better link which shows the complete study, carried out by Nestlé of all things.