Various sources give different recommendations for protein consumption when building muscle, from 1 gm per kilo of body weight (that's 2.2 pounds) to 1 grm per pound of lean muscle mass (that's body weight - fat weight), to anything in between.
Increased protein needs for repair and building are usually naturally met because of increased food intake.
Unless you are eating a high junk food diet, or a diet relying a lot on fruit, it's hard NOT to get enough protein.
The time during which we need to grow and repair the most (when we are babies), we consume about 4-6% of our calories as protein (through mother's milk).
I wouldn't recommend more than 20-25% percent (maximum) of calories as protein for health and fitness.
Also, I have no idea where I read this, but I recall seeing something about our bodies not being able to process more than about 20 grams of protein at one time (which would vary according to the individual. Somebody like Arnold S. in his prime would be able to process more because of his huge size, a petit woman, possible less). So downing protein drinks with something like 40 grams of protein means most of it goes down the drain. (The push for high-protein for muscle building is very much supported by manufacturers of protein supplements, who iinfluence what is written in bodybuilding magazines.)
It's also important to get enough carbohydrates, because if one doesn't eat enough carbohydrates to satisfy the body's need for glycogen (what the brain works on), it must convert protein to glycogen, which is an inefficient procoess, and uses protein that would otherwise go to building an repair (the reason why low-carb diets are necessarily high-protein diets).
Just my take.
