No, then call it "All you can eat, until we decided cut you off buffet". You want to do business, then make it a honest business. You can't put up an ad for all you can eat, and cut people off when you realized that the particular customer is that 1%. Now I agree, that you should not waste food, I have seen restaurant with sign that says "don't waste food, we will make it eat it all". That's fine by me, but you should not be able to limit how much people can eat.
Plus, most buffet restaurant already make money off of the 99% of people that only eat 2-3 plates (or less). So in a way it's similar to taking a gamble, they bet that the average customer will only eat 2-3 plates, so they already charge more for those two plates. But sometimes you lose and get an eater, then you should just stuck it up and let them eat.
It's not the customer's fault that cellular companies like ATT and Verizon did not foreseen (or underestimate) the demand for 3G/4G usage many years ago. With that notion they use unlimited data to get more customer thinking that it would be a great business model. Then when the whole thing blow up in their face they want to turn around the punish the customer? If anything they should fire the group of analyst that did the projection for the usage of the 3G/4G technology.
However you want to put it, it's bad business. If you advertise something you better make sure you can deliver. Nothing against you, but I just think business should be honest and live up to their agreement.