I think protein is very important. Protein and Amino Acids are the basic fuel for building muscle. Your body simply cannot build muscle without it. If you do not get it from your foods, then your body will try and take it from fat stores - which as we know - a gymnast does not have much of this!
I think the .5 gram per body weight is for the average person. For someone that is trying to build muscle (which a gymnast is) then the more common recommendation is .6 - 1g per pound. This is pretty difficult to get in a daily average diet alone. Consider this - a breakfast of whole grain cereal, a lunch of a chicken sandwich and a salad, and a dinner of say spaghetti with a snack of a granola bar and an apple. Sounds like a decent day of nutrition right? In terms of vitamins, calories, and carbs - sure. But protein - that is about 40 grams only total! Take your 80lb gymnast - at the .5 gram per lb recommendation that is right on - but for 1 gram per lb, you are only 1/2 way there!
I would think that a for a team gymnast that is normally in school for one meal and in the gym during the evening hours - this can be even harder... so I think a protein shake would be a good option.
I work out in a fitness gym - and so I am conscience of muscle building and my daily nutrition. I have a goal of 150-160 grams of protein a day and seldom make it. I drink a protein shake a day that gives me 20 - 40 grams of protein (one or two scoops). It is just a mix that I mix with milk. It is food and full of whey protein. Bog - I checked and this one has little added sugar- only 4 grams. It is Whey protein powder from GNC.
I know the following links are from "Mens Health" - but I think it still contains good info that would convert to our gymnasts:
Link Removed
Another article about proteins:
Guide to Protein: Men's Health.com
Basically you want a Whey protein and like Bog said - you want one with little added sugars.
I generally try to snack on high protein foods like almonds, sun flower seeds, cheese, certain nut based granola bars, etc.
As for gyms banning protein powders - I find this highly unlikely. Maybe things like Creatin - but not protein powders. It is not performance enhancing and it is not unnatural or damaging if you eat too much.