This is a very interesting article. And while it is true that cats in nature eat a high protein diet, don't forget they're ingesting the contents of the stomach of the bird or mouse - which has grass and grain in it. Also, cats do drink water. Finnicky cats often only like moving water - thus the water fountains. But for cats that won't drink, wet food often provides the hydration they need.
We let our cats free feed on dry food, and we feed them one meal of wet food a day.
After doing some research I am a firm believer in wet food. I switched my cats to a half wet, half dry diet in December and to all wet in January. Kolohe and Eric have had urinary tract crystals and need the extra moisture in wet food. Eric is also borderline diabetic and does not need the carbohydrates in dry food. Here's another web site discussing the advantages of wet food. http://www.catinfo.org/
I agree that cats need wet food. Their natural diet would only be about 5% carbohydrate (stomach contents of prey) and not the 30%+ found in most dry foods. Even though cats eating dry food do drink more water than those eating wet, studies have shown that overall they take in less water and have more concentrated urine than those who take in water with their food. Jaffa is on all wet with added water and Mosi has about half and half at the moment but I'm increasing the amount of wet and want him on all wet by the time he's 3 years old (he's 16 months now).
here's another article that helped convince me that wet is the way to go