I've seen people say that you shouldn't eat more than 0.8g or even 1g per kilo of protein per day.
But if you use the 40/40/20 macro-nutrient ratio on, say, 1700 cals for someone weighing 170 pounds, you will get 160g of protein which seems huge compared to 136 or 77 using the other methods.....
what do people think here?

I think the 40/40/20 breakdown is a proven way to structure your diet and get results. Theres nothing wrong with eating more protein, its essential for weight training and its the most satiating of the macronutrients.

I've seen people say that you shouldn't eat more than 0.8g or even 1g per kilo of protein per day.
But if you use the 40/40/20 macro-nutrient ratio on, say, 1700 cals for someone weighing 170 pounds, you will get 160g of protein which seems huge compared to 136 or 77 using the other methods.....
what do people think here?

In truth, 40-40-20 is just pulling a random card out of thin air and using it as a guideline. It's probably a good starting point because it ensures you are getting a decent balance, but there is nothing magic about the ratio. I could go on and on about the history of this, but I won't.

In a nutshell, ELITE ATHLETES who train long hours and need maximum recovery need about 1.6 grams per kilogram of protein per day, or about 0.8 grams per pound. Therefore, anything over that is just a waste of money. HOWEVER, I wouldn't necessary say it's bad for you - if you enjoy higher protein intakes, then I wouldn't shy away from them. While you most certainly are burning the majority of the protein for energy, it is a good security cushion to make sure you are getting the minimal amount needed for recovery / muscle building, etc.

Having said that, a more sane way to structure a program is to make sure you are getting about your body weight in grams of protein per day to cover those needs (and less is probably fine, body weight just makes a good security cushion), then divide your weight by around 2.5 to estimate fat grams (this would be whatever incidental fats you get from lean proteins, and then fats you purposefully add such as omega-3 = flax seed, fish oil, etc). Then, whatever is left over is going to be your carbohydrate needs. If you sit in front a computer desk all day and only train for an hour or less, then you probably just need your body weight in carbs. If you are an active athlete who bikes for 100 miles at a time and engages in various sports and are on your feet all day, you may need 3 - 4 times that in carbohydrate.

These are guidelines and can be adjusted. This is probably the first place you'll see the 2.5 divisor for fats but it's worked for me. At 200 pounds this is what it would look like:

200 grams of protein = 800 calories
200 / 2.5 = 80 grams of fat = 720 calories
Now, if I am going to do body weight of carbs then it would be 200 grams of carbs = 800 calories and I am on a 2320 calorie diet with around a 33-33-33 split.

I estimate fat higher than most because I believe it truly is key in managing blood sugar and recovering from training.

A bicyclist might do twice their weight in carbs, taking us up to 3100 calories and now the split is higher in favor of carbs.

A body builder cutting for a show might reduce carbs somewhat and favor protein fats.

Those are just ideas.

It is ludicrous to think that 40-40-20 works with every situation, high or low calories, etc.

Again, I know the history behind this and it is very flawed. It is not a rule set in stone. It is a great guideline to start with, but don't be afraid to tweak and experiment to see what works for you. Having 1800 calories verse 2000 will do much more for fat loss than worrying about 40-40-20 versus 60-30-10 or some other ratio.

Jeremy