Dog food is not good for the cats because it doesn't contain nearly enough
protein to fit their needs.  If they are filling up on dog chow, they may
not be geting enough of their own food.  Feed the dogs seperately where the
cats can't get at the food.

Really? Why is it harmful? What are your sources other that your vet?
Sometimes, just as for humans, a dog has a peculiar problem that makes
feeding him a peculiar kind of food harmful.

I give a cup of cat food to my neighbours' big dogs once in a while. And, of
course, it's desert to them because it contains more protein. Dogs do often
get along with a lower protein diet and it certainly makes feeding them
cheaper, but my feeling is more protein wouldn't harm, mainly that the said
proteins are in a large part of vegetal source. We feed dogs vegetal
proteins ans cows animal proteins. We're that crazy.

One of my cousins had a Pit Bull who was loosing his hair and looked
unhealthy. He owned a pet shop and was mainly selling IAM food. I suppose
that's what he was feeding to his dog. So he began adding some real meat to
the dog's diet and the dog got better.

Does cat food contain that much more minerals that could cause bladder stones?

GP

What about when your dog eats the cat food?
All my cats and my dogs eat each others food and so far, there has been no
harm, and none my vet can see.
We go through bunches of cat and dog food, so I guess  it's ok.