The answer is Yes and No depending on what sort of ham you are feeding your cat as a treat.
Processed, off the supermarket counter, ham in various guises may contain too much salt. Salt intake should be limited both for humans and cats.
The Association of American Feed Control Officials state that the sodium content in cat food should be limited to 0.2% and the National Research Council guidelines state that 42 mgs of salt should be the daily maximum.
Sarah Hartwell of messybeast.com says that if you properly cook raw pork it’s okay as a treat. It is best to avoid feeding raw pork because it may be contaminated with tapeworm (not sure how prevalent that is, probably quite rare).
I feed my cat the odd processed ham treat. The amount is limited and given infrequently. The conclusion is that it is alright to give a ham treat to your cat as long as the amount is restricted to avoid excessive salt intake. I’d suggest that if pork is cooked by the cat’s owner and no salt added then clearly more ham can be given to a cat. But even then the amount would have to be restricted because the diet would be unbalanced.
My thanks to Diana Hutchinson of tinpaw.com.