Actually, too high a protein intake can have detrimental effects on the kidneys. As we know, when protein is burned as a fuel, your body produced excess ammonia from all the extra nitrogen, which is toxic. Your body gets rid of this ammonia through the urine, making the kidneys work overtime, while at the same time dehydrating you because of all the water loss that accompanies the ammonia in the urine.
This dehydration leads to decreased muscle performance. So too high a protein intake can have many detrimental effects. I personally recommend 1 to 2 grams of protein per kilogram of bodyweight...depending on your personal situation.