I would like weigh in on this discussion.
First- RAW is optimum, if done right. However there are other great alternatives that lead to a healthy and happy ferret with less work and often less expense.
Don't fall into the "ferret product" trap. Many cat products are absolutely safe for ferrets. MOST ARE NOT! However, many are. Also, from the standpoint of their digestive morphology ferrets and cats are very similar. There is a good amuont of research tying the use of dry kibble in cats (and even dogs) to diabetes, UTI, and vomiting. The reason is that cats and ferrets lack the digestive enzymes that dogs and people have in our saliva, and therefore do not properly break down kibble. This makes me also wonder what problems (adrenal!) that may tie back to that same issue!
I use a large amount of natural balance and avoderm canned foods. I also choose foods that are low in fish because the fish can really bring out a stronger musk. I use some dry kibble as well, softened with hot water. I usually use either taste of the wild (grain free and 42% protien!) or VF complete (good quality with no soy, wheat, corn, by-product and totally fish free!). I find fish also causes issues in many ferrets that people may not realize, so I will often try to avoid fish all together.
Just my 2 cents!