How about blaming idiot people for obesity? If somebody is to be blamed it's them. It's ridiciulous that somebody would actually thing that fast food companies are responsible for obesity. No, they are not. I eat fast food few times a week and I'm not obese. I'm not even overweight. What is my key to success? I don't eat it like a fucking pig stuffing myself to the limits with burgers/tacos and then topping it with a large cola/milkshake (or rather sugarshake).
It is actually very easy to keep a track of your diet when dining in fastfoods - they provide detailed nutrition information on their products, so you don't have to calculate it yourself, like when you make food from scratch at home.