I agree with Gina that if they call it all you can eat there should not be a limit. I try to avoid these places too. Not because I lack the self control to stop but because I never feel like I can eat enough to get my money's worth. I don't think that anyone should regulate this(especially not the government). I think people should either learn the self control to not stuff themselves or not go to places like this.
Personally, I no longer eat at "all you can eat" buffets because no matter how hard I try, I always end up eating way too much and feeling terrible for it. With that said, I don't think there can be a limit imposed on the amount people eat because: All you can eat means all you can eat. If there's going to be a limit, then it can't be called all you can eat. If a limit should be imposed then it needs to be called something other than all you can eat. It's fiine if you can control the amount you consume, but if most people are like me...stay away or You will eat too much.