My take on it;
Following a good strict consistant diet is important, not for the sake of gains but being in a good routine eating-wise as well as training helps keep you motivated/focused. It certainly does for me anyway.
HOWEVER
As for protein intake for your average joe (i.e. all of us on here), my theory is that you need to take in as much as physically possible every day.
Every meal i think about protein first, so if im having a chicken meal, i know one small chicken breast isnt enough, so i make 2 or 3 instead. I know 1 can of tuna isnt enough so i open 2 or 3 instead.
If i get hungry at bedtime or at some point in the day, i have 80g of whey in a shake.
Some days i'll get 250g where i miss a meal for some reason, work/socialising etc... other days i'll eat 400g+.
I don't believe all the science behind bodybuilding/weight trainng/muscle building, some of it is very true, some of it is ridiculous.
If a 60kg man eats 400g of protein a day, 500g of carbs and 200g of fat and lifts regularly and heavy, then he WILL gain well. Maybe some added bodyfat but that can be removed with a tweak on the carbs/fat intake.
The point i'm trying to make is; Us normal lifters, who train for muscle and strength gains, not to step on a stage and compete should just eat as much protein as we can. It is sensible to monitor carb and fat intake in order to keep bodyfat in check but protein wise, get it in you and stop poofing about with shit you read online.